For all you people who don't want or need a shoulder rest, or who can buy a $20 rest from Amazon and it just works, I'm happy for you. I am not one of you. I've got a long neck, among other contributing features. I've bought Kuhn, Everest,Fiddlerman, Bon Musica, Wolf, and they all don't quite make it. When I got them in the best position for me, at an angle with the feet towards the back, they all had a tendency to slip off. I added a coat hanger wire hook with a pivoting disc over my shoulder to the Wolf, which really helped keep the rest in place but exacerbated the slipping off problem. I finally clamped it on with chin rest clamps, which solved the problem but was a PITA to take on and off. Not a biggie for me as long as my fiddle is hanging on a stand, but an issue if I want to take it somewhere.
So, browsing about the interwebs I stumbled across the Wittner ISNY. It has a base which attaches to the chin rest and clamps in place and stays on the fiddle. It's small, flat, and doesn't interfere with fitting in a case. An arm with a swivel joint that can move side to side and up and down clips into that. Another arm, the part that contacts your body, attaches to that, which also adjusts side to side and up and down. The foam rest pad snaps onto that arm. It is flat but flexes on the for snap points to fit your body. All in all, it is far more adjustable than any other rest I have seen, and steady as a rock. It unclips from the body, and will likely fit in most cases like that. You can take the two arms apart, even pop of the pad, to make a really compact bundle. Clip it back together in less than a minute if it is completely disassembled, a few seconds if you just removed the whole assembly. Your adjustments are not affected at all by taking it apart. I've been playing with it for a few days, taking it on and off, taking it completely apart and back together again with no problem. For me, I'm just going to leave the assembly together as it fits in the zipper pocket on my case just fine.
Added bonus, the shoulder hook I made for the Bon Musica just pops right on like I had designed it for this rest. Sometimes I stagger smartly. I works fine without the hook, but with it I can take my chin completely off the fiddle while playing, so viva la hook.
This the most expensive rest I have purchased so far, $68 total from Amazon, shipped from Germany, but if I'd have bought this one first I'd be way ahead of the game.
'Cajun Fiddle ' 4 hrs
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'Windsor Violin' 3 days
'Two versions of Money Musk' 3 days