OK, that's a good enough reason... The original 54mm wheel came from Wren in the first place you can't really do any wrong here.

Are you sending the engine to WREN for professional balancing? If not there are a few guys around Canada that can help you out if needed... Ed M, myself, and a few others I think. Internationally, you could send it to Carlos, Wren, ChrisM in Australia, etc. After the smoke clears, my system will be able to detect a felt pen mark on the shaft... Being that the imbalance function is parabolic, its critical on a 160K RPM engine! Its well worth it to send it to Wren or someone with the equipment, your bearings will thank you.

As far as the ECU is concerned... I'd recommend the manual / full auto FADEC by Gaspar, The GB Hobby unit, or our new TEMS ECU. I can have a full auto TEMS tailored to fit the 500 quite easily as it is almost exactly the same engine core as the PST J600. The PST just has a slightly higher mass flow because of a different compressor wheel. AMA approval for the 500 might get a bit sticky though. We plan to eventually have the TEMS approved with a bunch of 3rd party engines. Don't know the story for the GB or the FADEC.

Good luck, sorry to hear about your misfortune.

Kelly