I haven't checked the MODERNIZED e-mail in some time; I just checked it now, but I don't have a message in here from you recently. If you tried to send us something, please resend!
The HP thing is actually pretty simple. The way d20 Future has mecha now, HP is determined by size, Hardness is determined by the mech's Supterstructure, and the mech's equipment bonus to Defense is determined by it's armor (if any). The way Rednecks & Mechs will have it is Hardness will determined by the mech's Armor, and HP will be determined by the mech's superstructure (this gets really fun when you use a vehicle or random scrap for a superstructure).
I doubt I'll take advanced physics concerns into consideration, like thrust versus weight and such. Rednecks & Mechs is a game that hinges on a rediculous premise, and is meant to be just plain fun. Hard physics can be fun, but more often then not, they can obstruct one's enjoyment of the game.
Don't get me wrong; hard physics do have their place in gaming. Just... not in Rednecks & Mechs.