Hi, appreciate your interest!
Sorry, I do not have options to test GLASS, and also away from my SIM PC.
Tho I this can share:
0. Do all above.
1. !BACKUP! your XPlane12\Aircraft\X-Aviation\Mitsubishi MU-2 Marquise v2
2. Open xsMU2B60_GLASS_XXX.acf with PlaneMaker
3. Go to Standard -> Weight & Balance -> Payloads
4. Set all numbers and options exactly as shown on attached photo.
5. All done. You are Fantastic!
6. Have fun.