I bought a UV filter for my FZ38/35 the very next day after I took
delivery (back in December), but only to protect the lens.
I like to use the macro capability, but it can also easily lead
to accidental scratching, thus my belief that a uv is necessary
on a superzoom with a "long" reach
(Basically if I scratch the lens, I may as well throw the camera away).
The FZ 38/35 uses a 46mm thread and fits on the lens extender itself,
and not the barrel. It will add additional 4mm to the lens extender
length, but the lens cap will still easily close on the barrel with it on.