Not sure I understand your first question. If you choose to use a shroud, and insulate it either at both the top and bottom or just at the top, that's OK providing the chainplate is not shared with another shroud and the spreader has an insulated fitting where the shroud passes thru. There's no need for a halyard in this case, since the shroud is permanently in place.
By "alternate backstay antenna", I mean an antenna that you fashion from a length of wire, preferably insulated s/s lifeline because of it's strength and resistance to the marine environment. It's THIS antenna that you'd hoist with a halyard, and tie off to your pushpit.
Yes, 23' or longer is fine. Longer lengths tend to favor the lower bands, while shorter lengths favor the higher bands.
The tuner is going to be costly, and there's no good way around it. While the LDG and other auto tuners can be had for less than the Icom or the excellent SG-230 tuners, they are not as robust and over time will be sure to disappoint.
Only way I know to have a decent installation with a manual tuner near the rig is to put a high quality un-un (a type of balun) near the base of the antenna and feed coax back to a manual tuner near the rig. You might save a couple hundred bucks that way (a good Un-Un is about $85, a decent manual tuner about $100), but unless you enjoy tuning every time you change bands you'll be better off with an auto tuner. Personally, I'd spring for the SG-230 ($499 new) which will work with ANY HF rig and is superior in several respects technically to any of the Icom tuners.
Last edited by btrayfors; 09-10-2010 at 10:29 PM.