[Amps] Inexpensive variable air cap for amps

[Hsu]

Hi, 
 I just purchase some teflon film,the price not too expensive($30/kg). I think I can insert it into low volt/small volum variable air cap as high volt plate tuning cap, I think teflon film  with larger ? than air, the cap should be smaller ,even we can use a  cheap receiver tuning cap as amp's plate cap if it can hold enough RF current. does anyone have this  experience?
                        73! Hsu