Bruce,

On my 6.4 I couldn't get over 5,500 rpm with the 26-10 MSC. Cutting it down 1/2 an inch only gained another 150 rpm. Even Gary agreed that it was not the best prop for the engines' power band. Going with a Menz "S" 27-10 and the rpm immediately jumped to 6,000 plus a little with an immediate and very noticeable improvement in thrust performance and a cooler engine. BTW, the base elevation of the rpm tests was about 450' MSL. My normal flying field has an elevation of about 1,300' MSL and the MSC was too much prop for the 6.4. I've got a Biela prop at the house but it appears that it will be quite some time before I get to try it. Looking at the Biela, it has a blade width that lands between the MSC and the Menz.

Pat