CJF:
While its fine to say you shouldn't lose any...
sometimes sh!t just happens.

I minimize losses, usually to zero, by using anhydrous lanolin as the sizing lube, and I mean very sparingly ie wiped on with the fingers like you're wiping it off...
and rotating the case ~180 degrees between compressions of only a few mm each time.

That is, size a couple of mm, back fully out and rotate case in shell-holder, then size a couple more mm, backing off and rotating again, and so on until fully sized.
Maybe a dozen or more compressions per case. Actually takes less than a minute per case.

Everyone does it differently I suspect, but that's my MO for what its worth. Hope it helps.
Cheers