PITA if you're out and about. Why do they do that? It seems so inane! I don't understand why they can't just twist off and fill from bottom. I really wanted to grab a lot of those. There's still a sale on stm, I already have two, but I will grab two more. I think they are dependable tanks.
Is mounting the coils on the kayfuns as easy as stm? If there is a little difficulty I won't mind.
A Kayfun is easy as they come to build on.
for myself, bottom fill is not an issue ... I never have to refill when out and about.
I always take 2 ProVari topped with Kayfuns when I go out ... and If I'm gone overnite, I bring extra batteries, juice, build tools, etc.