Getting too big ?? If they fit good at first, then seem to get too big is there a possibility that the metal threads on you're Taifun base are a bit rough and acting like sand paper and wearing the thread material away from the Acrylic
tank threads ? chanel, I have been using the same Acrylic tank on my Taifun V2 base (same base) ever since I have got it, and it still fits tight (though I do have to watch out about cross threading the darn thing, in my case it would be very easy to do). How long do you get out of an Acrylic tank before it just gets too loose to screw on to the base, and are you using the same base all the time ??
Edit: I got the same Acrylic
tanks that you and petemoss recommended that I get when I was looking to set up my first parts Taifun. Maybe FT is getting some sub-standard Acrylic
tanks in, there's always a chance of that happening.