Anybody done this?  I've got a few Chinese 5-rounders and I understand that if you trim the followers, you can use them as 10-round mags.  Any instructions on this?

it will b more like 8 if you go for 10 you will have probs

As you can see from the below pic there were two types of Chinese 5rd mags that were imported. A short one and a long one. The follower of the short mag is the same as the follower in a 30rd mag.
The long 5rd mag accually a 10rd mag that has a longer follower to limit it to 5rds. Cutting the long follower to the same length as the follower in a short 5rd or 30rd mag will allow it to hold 10rds. Cutting the follower in a short 5rd mag so it will hold more rounds will result in the follower twisting and binding as it moves inside the mag body causing failures to feed.

i trimmed the follower in my mag to hold 10 with no problems at all and it's one of the short 5's.  i also tried the follower in a 20rd mag but it only held 22 (i never did try a 30).

Take 1 inch off the follower to get 10 rounds in a 5 rounder.

I trimmed a Chinese and got 11 round capacity but loaded only ten, this was a mag I got from Norinco with a Mak 90 rifle about 14 years back.
A handy size.

put the tapco followers in and they will fit 10 rounds