C4.1 gearbox tight

[ASR]

Just building my c4 up at the moment, just finished the gearbox. When nipping the cap heads that go through the box and into the motor mount alot if resistance appears?.

Slacken these cap heads off a touch and it's as fee as ever, (but the screws are offering little in the way of clamping the box together).

Everything is cock on mechanically, bearing etc, just wondered if there were any areas of the box that need sanding etc.

Sorry if this question had been asked before, I couldn't find the answer.