If he has his OWN stock library, then let him market your work, you keep the copyright, and split the fees obtained.
As someone else said, a historical norm has been 50% of fees to stock libraries (for doing the marketing, negotiation, contract etc) and 50% to photographer. On that basis, you'd probably do the shoot at either your expense or with him just covering the costs.
After that it's a win/win situation:
Good for him as you've supplied bespoke images for him to host in his library.
Good for you as you retain a share of the potential usage fees.
Even better, you now have a long term partnership when you can combine your skills (your unique skydiving photography - and it IS unique when you take a moment to step out of our skydiving 'world') and his marketing skills.
A note on the fess that the images might generate: for a small editorial magazine 1/4 page non exclusive could be less than $100 single run. However full size, exclusive rights, for commercial advertising could be into £1000's.
Gordon Hodgkinson
http://www.gordonhodgkinson.com
Blue skies!
Gordon
Beware of advice from those with more posts than jumps ;-)