I was thinking the same thing. I hold all the ASA's as well, yet, i own a 40 foot boat. If you came to me with your resume and asked for a week on my 40 footer i would ask for a serious check ride. I think that if you had asked for a 30 footer they probably wouldn't blink. Going from 30 to 40 boat is a jump.
Given that you had crewed several times i would take this into account. Some letters of recommendation from the Captains of the crewed boats might help as well. IE Docking, mooring and sail skills.
Ownership of a similar boat that one wishes to charter and experience on it trump all the certificates that one can possibly earn. Let me share my last experience with a certified ASA instructor from about 3 weeks ago. NO, I am not knocking ASA in any way but rather what happens when lack of practical "big" boat experience meets paper certifications.
I was hired to do a one day familiarity trip by the charterer on a 44' Jeanneau. The charterer is a recently certified ASA instructor who sails regularly and teaches at an inland lake on 20' keelboats. Being a cautious guy with his family on board, he requested a skipper for the day to get used to handling a boat much larger than he was used to. He had zero ego and was an absolute sponge absorbing info about new to him systems like the generator and A/C systems. I asked if he would like to do the safety briefing before departing the dock to which he eagerly agreed. I listened and added info as needed but overall he was very thorough covering MOB, fire extinguishers, life jackets etc. He handled the boat pretty well once we had left the dock. During lunch I asked if there were any specific things he would like to cover that I hadn't already. He asked for a surprise MOB at some point to see how his crew would handle it. Most of his crew had sailed with him, one gentleman had never sailed before... The instructor's daughter was at the helm doing an excellent job sailing upwind in choppy conditions. When everyone was focused on a turtle ahead on the starboard side, I tossed a PFD out the port aft and let it get out about 50yds before yelling man overboard!!! I immediately said that I lost sight of them but they are in an orange life jacket (my subtle signal for others to spot them and maintain a visual, at this point I lay hands on the horseshoe life ring so it is not tossed) and started a stopwatch. At this point the non-sailor/boater immediately pointed and said that he sees the MOB. This guy was a machine, he never stopped pointing throughout the "ordeal". Next we did nothing...30 seconds still doing 8kts away and we did...nothing...1 minute into in and no actions taken. I finally said that I really didn't want to loose the life jacket and directly asked the charterer what his intentions were before I took over the helm and got the PFD myself! Granted now we are 200-300 yards away making 7-8kts, the course still hasn't been changed, no words other than mine have been spoken! The charterer finally snapped out of it and had his daughter change course which soon had us in irons and then more or less hove to. We are now 2:30 into this and haven't really even begun to proceed towards the MOB. Eventually I suggested the best helmsperson take the helm. The charterer took the helm and began instructing the crew to ease some sheets off winches and eventually got the boat moving generally toward the MOB. 4:00 into it we have done some sort of a convoluted figure 8 and are coming into the PFD on a near beam reach making nearly 9kts. After repeatedly hinting that we are carrying a LOT of speed a crewmember is sent to the rail to grab the PFD. The wake from the bow wave literally shot the PFD away from the hull as we flew by.
Strike 1 at about 5:00. A real figure 8 is immediately attempted but made too tight to get within 20' of the MOB. Strike 2 at about 6:30. Charterer learns from his mistakes and makes a perfect approach nearly stalling the boat on the MOB while furling sails. MOB is recovered stopwatch indicates just under 9 minutes. The person with the least amount of experience on the boat has never once stopped pointing at the MOB and finally lets his arm down. Five hours earlier he didn't know what a MOB was or what to do about it. Clearly he was paying attention during the thorough safety briefing at the dock. Get that guy a beer!
During the charterer's safety briefing at the dock regarding MOB procedures he seemed to be repeating a section of a manual verbatim. I interjected numerous other options to consider rather than, or in addition to, sailing the standard figure 8 such as:
Hit the MOB button on the chartplotter
Start the engine and quickly furl sails, motor back to retrieve MOB
Hop in the dinghy and get the MOB
Reviewing the drill, all agreed it was an unacceptable amount of time to get close to retrieving a MOB. The charterer said his mind went blank. He'd never had a non-planned MOB drill. He was used to the smaller, slower, more nimble keel boats on the lake. He wasn't used to the wind speed or sea state we were in. He never considered putting the most skilled person at the helm before it was suggested to him. He'd never been on a boat with a "real plotter" and forgot to even consider hitting the MOB button. He was used to sailing boats without motors or that had very small kicker motors and never thought to use the 75hp that was available to him.
I know this gentleman is NOT typical of the very skilled ASA instructors I have been around. Despite all of his credentials, he clearly did not have the experience necessary to handle an unplanned fake emergency on a 44' boat with moderately experienced crew (they had only been on small lake boats too). Since this event is still fresh in my mind I thought this a good chance to pass it on. These are the sorts of things that keep me awake at night whenever I OK a charter guest who struggles a little on a sailcheck.