Glue for thick veg tan leather

Hi all,

I'm wondering if anyone can recommend a good glue for veg tan?

I'm working with 3.4mm shoulder from La Perla Azzura. I've tested a few glues: Evo-Stik Impact (solvent and solvent free), Intercom Eco Stick 5019N (which is suppoed to be stronger than the 1816B), wood glue, and even superglue (as a last resort!).

With the Evo-Stick, Intercom, and superglue, I am still able to pull the glued pieces apart easily after 24 hours (under weights or clamped). Wood glue seems to be better, but still not ideal.

I'm skiving the two surfaces to be glued, and scratching them up with a knife before glueing. Can anyone recommed a more suitable glue?

Thanks, Hannah