Shok,
I looked at this stuff for my own runway on a piece of property I bought. As I understand it. this stuff was never meant to be permenant, and after it starts to degrade the soil will wash. What you really have to do is to put down a good foundation and get someone with heavy equipment who is willing to take the time to work the dirt down, pack it firmly and get it good and level. I had many loads of top soil hauled in, and was told that sand needed to be put down before the Petromat. When I talked to the Petromat dealer he told me this stuff was designed to go down prior to paving, and that was what is was designed for, when I told him what I wanted to do with it, he said he figured it would only last 7-8 years at the best.
Maybe you could talk your people into reworking the runway and adding a base of dirt or top soil if they insist on grass. With a little work the grass sould be as good as the Petromat, look at Mac Hodges place down in Georgia, it is awesome and you could fly anything off of it. I managed to find a golf green reel mower at an affordable price that I plan on keeping my runway trimmed with. You can cut the grass down to 1/8 inch, that is like Astroturf, but the ground needs to be prepped beforehad. good luck, sounds like you jet guys are the minority in your club, and you may lose out.
Tommy