So, I just bought a 543...

That is correct. The springs in the E-Street are for the roller and I would indeed be swapping those to the RPM heads. I disassembled the engine (the short block is intact yet) and visually looked things over last Friday and things look well so far. With the pistons in the hole where they are and 84cc heads, the compression ratio should be approximately 11:1 according to the 440source chart on their website.
I just mentioned checking c.r. to make sure he wasnt running alcohol for a 14 1/2 to 1 motor, or something like that.