A star ground scheme will work fine, be sure to follow the guide lines here: http://www.valvewizard.co.uk/Grounding.html

The pots you have should work fine, be sure the connections to the pots are correct and that there is no open grounds. Soldering to the cases (or a brass ground plate)is no problem with a properly cleaned and tinned 40w or more iron. 60w + is better.