I don't want to further derail your thread with my other opinions (and I am sorry for my participation in getting your thread so far off track), but if you want to give it another go you can try this to technique to flatten them for very little money at home:
The most expensive thing will be a sheet of glass big enough to do a header. VW guys (and obviously small engine guys) have been using this trick forever. Your local body shop can probably sell you some "long" sand paper off of a roll (for using on body boards) to get you the coverage you need. The bodyshop stuff will also have an adhesive back which might be nice for this project. I would still use it wet. FWIW, I bought a few rolls of 180 and 250 (I think 100' rolls?) for about $40 a roll. Body shop will probably just GIVE you a few feet.
Total cost will be approaching $50 by the cost of glass alone (could always get some out of an old window too). BUT... You'll have the glass in the future for other projects.
I still recommend quality header gaskets no matter what.