underseal and chassis tube caps

Just getting to the end of a tidy up (well snows is here so what better time to do this!)

1. Anyone found plastic caps for the chassis cross tubes? Seems if you filled the tubes with Dinotrol/Waxoyl and then capped with plastic tube caps it would stop the crud getting in and hence rust.. anyone found the right ones?

2. Underseal or Schultz
OEM is heavy rubber compound Schultz and it did OK. But it traps moisture and then corrodes behind so you have to chip it off to deal with rust. What to put back on ??? Dinotrol/Waxoyl do black wax with anti corrosion .. I was thinking of doing fluid followed by black wax coat as MOD do.. but I do like the loading of lips done by the factory.. I have seam sealed where I have to .. anyone any thoughts?

3. Paint .. found an alternative to POR15 and Rustbullet =
http://www.bilthamber.com/electroxbuy.php
zinc rich primer .. best Practical Classics rust test 6/6 compared to 3/6 for POR15 & 4/6 for hammerite
.. this is poor mans galvanising .. the other two just seem to be a very high adhesive water proof barrier.. 2 ways of doing it.. comments?

4. Black on bumpers/trim etc.. anyone got any paint codes?

back to painting!