The Prof said:-
Where does the joint fail (ie is the glue residue on the aluminium, the leatherette, or both? Heat could well be your problem. Most glues soften with heat, and surprisingly little at that.
My experience is from making guitars and ukuleles, ..................................
ooooh another Ukulele maker.
Look combining pastimes !!!
But back to serious chat about adhesives (apparently not supposed to say glue)
The Evostic attaches to the aluminium like sh*t to a blanket as I found out yesterday when trying to remove the residue before starting again, having said that there is also glue still attached to the vinyl in most places. It seems to be at the edges of the trims where it seems to shrink back, peel and then I guess over time the glue re-hardens and you end up with trim material just sticking out at various angles from the metal.
I am going to retry with a "high temperature" spray on contact adhesive, turn a lot more of the material underneath and make sure there is glue on both the top side as well as the underside of the aluminum and make sure it is touch dry before bringing the two sides together.
Enjoy everything - Life is Short.