Dar, or David, or Pe:
With a new MVVS .49 (purchased in Canada) the head is all blue, with no cylinder insert to be changed. (this was a surprise even to David). So, with no insert change to allow for 15% nitro fuel, how many of the thin shims (or washers) do I need to use? Why did MVVS discontinue the insert using head? Was it only to save money? Will shims not be more liable to leak?

With a new MVVS .26 (also just purchased in Canada), it comes with a removable head insert, but comes with 2 shims. Do I use this supplied head and insert with both shims to allow use of 15% fuel? - or should the engine have been supplied with the 15% head insert?

Thanks,
Bill O.