I also sail Hobie 16's, T2s, Nacras, TriFoiler, etc., etc. yes these are all higher performance boats than the Islands. But in any case, once you cleat the mainsheet, you are not going to keep your sail in trim on a specific course. Then again, if you're just cruising around, you don't need to. I understand that.
Here are the three positions you can use on a horn cleat - cleated, just like being cleated on a camcleat. Half-cleated, which is with 1/2 turn around the cleat. This takes about 95% of the pressure off your hand-arm. You can then effectively hold the mainsheet with just two fingers if you like, even in a blow. But... if you release those two fingers, the mainsheet will slip free. Then you have uncleated, which leaves the sheet entirely in your hand with full sail pressure on you. So three options rather than two. And... unlike the auto-camcleat, you will never accidently cleat or uncleat it. No angle to worry about. It's right there next to your hand.
Please understand I'm not advocating that everybody with an Island must do this. But I have found it so much better than an auto-clam cleat that I think many who try it will decide as I have that it's the better all-around set-up for the Island. If you know flat out that's it's not for you, fine. But others who may be reading this and looking for an alternative to their current set-up might want to give it a try.
So, in my opinion, the horn cleat next to the seat gives all the advantages of the current camcleat, plus a 3rd option, with none of the disadvantages of bad angles, distance, accidental cleating or uncleating, inability to uncleat, etc., etc. If you'll go to this video and forward to the 5:10 mark, you can see me explain it on the video:
https://www.youtube.com/watch?v=VGjCUREoTwY