do you have a large cold surface you put your canvas on post-coating ?
that might also help with your frilling issues. at least with glass it helps ...
and luckily you don't have to make sure your surface is level ... the cold
chills and sets the emulsion.
i would try going against what the manufacturer suggests and do a test with canvas with the hardener in the fixer instead of the developer.
and don't use stop bath. if you can find and alkali fixer with hardener that would do you well too ... liquid emulsions seem to like alkali
no matter what you will have extended washing times because of there being hardener in the mix. if you use fixer remover / perma wash you can cut your
washing time to a minimum.
make sure you use a COLD developer ...
for the metal, i get it coated with an enamel paint. the emulsion sticks right to it and there don't seem to be any problems ...
good luck with your tests !