Cheers for the well wishes, lads. I'm hoping to have more to share soon now that the internals are all sorted out. I took a few evenings this week troubleshooting the electronics with Luke, and spent this afternoon adjusting the servos and drivetrain. We now have 100% functionality!
It's got the full range of elevation (-5 to +18°) and traverse (+/-12°). Track tension could do with a bit of adjustment, but it seems to be more of an issue on carpet than dirt or grass. The xenon flash looks great through the muzzle brake and is exceptionally bright, but the camera doesn't pick it up very well. I'm also very impressed with the PDSGB, it pulls like a train. The tank has no trouble steering on or climbing over anything, and drives nice and straight without the wobble or gentle curving I've experienced with regular gearboxes.
It's a shame the TCB is out of production for the time being, it's easily the nicest-driving board out there. I'm glad I stocked up on a few while they were still available from HobbyKing.