SB, first off great start! Cockpit looks perfect! As far as printing seatbelts, ajd3530 just hooked me up with a gentlemen who lives in the same town as me (I know what are the chances!), anyway he runs a sign making business and prints off sheets with Luftwaffe, US, and British belts on them (1/48 & 1/32 scale). I just picked them up last night and haven't been able to try them out on a build but you can take a look at them on ajd3530's build over on the Mustang GB pg 33. Just another possible option. Keep up the great work!
-Andy