This is actually the thinest I've heard about ! I do have fiberglass core GT2 myself that is thinner than the stainless steel core, but it's 1.5mm not 1.3.
I'll upload in a minute a new body. Could I ask you to tell me if the fit will be better ? I've designed it with 1.3mm for the toothed groove and 2mm for the folded groove.