I have a full sized 3v 1930s Hohner Club. It is a very nice box with a thumb groove along the keyboard which means there is no thumb strap. It seems more like a piano accordion than a diatonic; being both tall and long, it requires two shoulder straps to square it on the torso which is quite different than the 'fire from the hip' portability and ergonomics of the lighter Pokerworks and Erica models. You can almost sling them around one shoulder like a camera bag.
I don't like the groove, my hand being accustomed to the thumb strap. I'm thinking of fixing a thumb strap to the back of the keyboard via a discretely drilled hole which can be filled without too much remorse if I don't like it.
But is the Club's keyboard too long to make this a practical arrangement, i.e. being able to reach the far ends of the keyboard while still anchoring the hand? It's my largest box and I don't often see them with thumb straps, I'm thinking this is for a good reason and I may be putting myself out. Any ideas? Should I just learn to stand with two straps and play with a free hand or is adding a thumb strap a worthwhile investment? Anyone ever done this?
edit: FWIW the box has been declubbed and retuned to G/C with a row of convenient accidentals.