Going to be doing a lot of towing, starting tomorrow. I'm leaning toward leaving the engine on the dinghy in calm water, using two floating lines from my two stern cleats to one point on the dinghy. A ring mounted below the tubes on the bow. I'll probably keep it really snugged up to my boat. I can remove the engine and mount it in my stern when thins get rough. AND when they get rougher still, I'll pull the whole dinghy.
What do you think about my plan, and what do you guys do?
I forget what size engine you have, but anything more than the smallest OB is gonna increase the drag of your tender considerably... Just one more of those factors that wind up contributing to people sailing less, and motoring more, in marginal sailing conditions...
Your plan of waiting until it starts to get "rough" to remove the motor, or bringing the dinghy aboard if it gets "rougher still", is NOT a good plan, at all. No need to ask me how I know this

On a boat the size of yours, depending on the size of the engine, could be a good way to have either the motor, or yourself, wind up in the water. Never, EVER tow a dink with the engine mounted unless you are absolutely certain your trip will be completed in benign conditions, or are sailing in protected waters where you can easily find refuge where you can sort things out... Sure, it's a PITA to remove the engine every time you move, or bring the dink aboard for all but the shortest trips, but it's almost invariably the right thing to do... The conundrum of whether to Tow, or Not to Tow, is one of the best arguments in favor of modest, easily managed size and weight when it comes to tenders and OB motors. And I'm afraid many cruisers wind up often doing the less seamanlike thing, simply because their motors are of a size not easy to manage, and it's simply too much of a PITA to do the right thing
I put a snubber in my tow line to minimize the snatching loads that can be put upon the tow ring. Many inflatables have a pair of rings each side of the bow, you can distribute the loads, and minimize yawing a bit, by using those instead...
Whenever I tow my inflatable, I always use a secondary back-up tether fixed to a hard point... Probably the most secure way to tow an inflatable is with a line or pair of lines made fast to the transom, then taken forward underneath the boat (taking care to minimize chafe at the bottom edge of the transom), and then run through the tow ring(s). If your tender should ever capsize while underway, there's a very good chance the drag will become so massive that a tow ring glued onto the tubes will be torn free, and then the recovery of a capsized dinghy can become a difficult proposition...
Most RIBs have a thru-bolted padeye near the bow that is by far the best point on which to fix a towline. If yous lacks one, and you're planning on doing much towing, I'd suggest you add one. It will also be the best lifting point for bringing your tender back on deck...