Hi Scott,
I have tried a few different ways to drill the holes in the ribs but the best tool I have found are these cheap diamond coated hole saws from China. I pin and tape the ribs together, mark the hole using my rib template and stack drill as many ribs as the tool will handle. I use the slowest speed on my pedestal drill but I don't think the cutting speed is very important.
https://www.banggood.com/10pcs-5-22mm-Diamond-Hole-Saw-Drill-Bit-Set-Tile-Ceramic-Glass-Porcelain-Marble-Drill-Bits-p-1116959.html?rmmds=detail-top-buytogether&cur_warehouse=CNThe OS 15 CV-R(P)-T buggy motor was a limited edition engine with a turbo plug head insert and an alloy back plate instead of a pull starter. I cut the cooling fins off the head on a bandsaw first and then machined it into a clamp ring in the lathe. The spinner assembly is off a MDS -UCTKAM 15 piped C/L speed engine, the Cox Conquest assemble fits OK but I found you need a OS 15 LA end float shim behind the prop driver to stop the bearings from being preloaded. I had to machine up an adapter to secure the spinner to the crank with a 3mm bolt and the stepped propnut is a modified OS part , I machined up the venturi myself and the needle valve is a Brodak unit.
If you do not have access to a lathe and want a little horsepower there is always the NOVAROSSI RFX15TV at US$219 already kitted up for FF.
http://www.novarossidirect.com/RFX15TV_p_3273.htmlPhil