OK it's not so much as a solution, but seemingly an example...
The 2014 Street gsxr 1000. The endurance bike.
Use that, with a 'Disengage Max Torque' value of 650, and thats as close as GPB has been to a seamless shift.
So for those developing Grand Prix Machines with a seamless box, (moddders and piboso alike) I recommend trying this GSXR out first and see how that box is modelled, at least until seamless shifts are in GPB