To me it would depend on its intended purpose...(class-racing, head-up, etc) Because I've seen an 'ultimate' rotary engine too so, I'm just saying perception is relative for me anyway. But, if your fishing for ideas/opinions for your next Head-up engine because you want to be competetive then ( ) I would use an engine designed/engineered for racing with the foundation to seal and integrity to live at higher power levels and lastly used commonly enough that you can get a variety of parts for...e.g.- R3 W?, PS Hemi, R5.