Fixing top tubes

jv she's nearly built now, just waiting to borrow thebricks bb tool (cheers mate). couple of issues though, i have the shimano 600 stem with the hidden bolts and the plastic cap - cant seem to get it tight enough, any ideas?

What bars are you using? They might be 25.4 whereas the stem is probably 26mm.

also got a lovely light rolls saddle, anyone know what i can put on it to protect it from denim transfer? as a reformed sneaker head i should know this

Is it white? There's not much you can do to stop denim transfer that I know of. Suppose there could be a spray or something, but I doubt it will stand up to saddle friction, rain, sweat etc. Maybe just wear lycra or chinos?