WOW. Thank you, Scottyballs!
I had been meaning to get round to buying some blue foam, as my Tornado doesn't work well with standard cartridge filling. By chance, via a link from the Totally Wicked forum, I found this. I only read the first page of the thread, but my impromptu mod works a treat.
I didn't have the rights tools to hand, but I made one in about five minutes using a pair of kitchen scissors, tweezers and the middle bit of a Q-tip. I didn't have a thick straw, so used two lengths of Q-tip (2mm), one each side, to support the plug. I cut the cartridge cap with scissors without even marking it - jut cut off the thicker edges and trimmed til it fit, then stabbed a cross in the middle with the tweezers (that didn't work first time, got a burnt taste, so made the cuts a bit bigger - and hey presto!). No leaks, no floods, and a constant vape.
I was getting so few draws out of a cartridge (510 type) that it made life really difficult when about and about or driving. Problem solved, I think
