There is a very good thread on this site about converting Tiger daggers for the H18, you might find that useful.
There are no H20's around here, so I cannot help you with dimensions.
What I do know is that two years ago, I came close to buying a WildCat (and I should have!)
At the time, the cost of one new WildCat dagger frightened me, at US1,600 each.
Good luck with your endeavours.
1989 Hobie SX18 Sail # 1947 "In Theory..."
'Only two things are infinite, the universe, and human stupidity. But I'm not sure about the former.'