I'll try to address the queries that I have some info on:
1. My last five or six mains have been loose footed. 'Nuff said.
2. Some sailmakers like to add some roach on the foot in a loose footed sail. Never saw the advantage of this practice and don't recommend it. Otherwise, no differences in dim's.
3.The over the top leech line is good in that it allows adjustment when the boom end is out of reach. Has a bit more friction, but has worked will for me (62 M^2 sail). There will be a gap in the luff area sleeve at each reef point, with an attendant tiny clam cleat. One tensions the line whilst reefing. The cleat is oriented so that when you shake out the reef it releases the leech line automatically... pretty cool!
4. A loose footed sail does not have a shelf.
5. The need for a cunningham is not changed by being loose footed. Most cruising setups don't bother, since no one cares how long your luff is or how high you hoist it, thus obviating the need for the cunningham.
6. A slug at the clew would tend to hang up and make adjustment of the outhaul
more difficult. Many sailmakers use a strop of heavy webbing around the boom at the clew which is usually at the attachment between outhaul
and cringle. The strop slides back and forth with the clew as you adjust the outhaul. Cheap
7. Lots of different opinions on full vs short battens. The full ones are heavier, add loads to the luff cars at their ends and cost more. They (in most folks opinions) help maintain sail shape and add significantly to sail life in the cruising environment
. They do a better job of supporting roach area in the leech, especially near the head
of the sail, and this can add to the performance on all points of sail. They markedly reduce flogging when reefing.
On our main we have the top three full length and the lower two about 1/2 the width of the sail. This has worked well for about 35,000 miles, and I think that when we replace the sail I'll do it again.
8. I can't give knowledgeable advice on these materials.
9. All of the plastic slugs/slides that I have seen are Nylon. They work ok, but at the headboard I use metal ones... the Nylon just isn't strong enough for the loads imparted there. If you have your reef tack points set up right there is little or no load on the slug there... the loads are taken out by the reefing hook, or whatever you use to secure the tack.
So, that is one cruiser's opinion set. Others may disagree. Hope that it helps the difficult decisions ya gotta make in getting a good mains'l.