i had that very problem with a pro25
i had to deal with a pro25 for a while as a kick mic and hated it--it was/is the only rental available in town, so it was that or an sm58, and you take what you can get......
.....what i got was that i couldn't get the pro25 close enough to the batter head of the kick (in order to get that nice beater slap) and not have it distort (clip) on me. you could watch the levels on the board and while the levels on the board stayed happily in the green, you could hear it clip in the phones. the closer i got to the beater head, there it went.....further away from the beater, and it went away. it was the mic that was overdriving in this case--could be the case for you too, as you sound certain all of your levels are ok.
there's no simple answer to this question (well, there is....see #3 below).....but there are a couple simple suggestions/fixes you could try:
1. even though you're sure it's not clipping your input, use a pad and attenuate the signal buy 10 or 20dB. if you don't have one on your mixer or 1010LT, try an inline pad instead (shure makes one for around $40). see what that gets you.
2. don't put the mic so close to the beater head and learn to live with the sound you get with it backed off some.
3. use a different mic.
i went with option #3. i really didn't like the sound of the pro25 when backed away--i prefered it clipping and nasty to what supposedly "sounded good" when backed off the head--sounded like a really dead basketball (and sounded that way on both my late 80's pearl export w/2 heads and mid 60's ludwig with a single coated). i picked up an EV RE38 for cheap used and am glad i don't ever have to worry about using that pro25 ever again.
if you dig the pro25 or it's all you've got (or all you can get), then either employ a pad or be happy with the sound you get with it backed off a bit. for a cheap $50 alternative, you might want to check into the CAD kick mic they have over at musician's fiend--that mic has gotten good marks from some around here (as has the pro25, as surprising as that is to me). and for $150, i really like the sennheiser e602.
wade