I have one of these drilling blocks. IMHO it is faster than using my Proxxon with the Block, AND more accurate, let alone about 25% of the cost of the Proxxon with the attached table (a necessary addition).
GoatBoy -- (or someone who has the same skills), you could easily sell 50 of them within a month.
However, the steel inserts are absolutely a necessity. DerbyWorx is bound to duplicate this item, but I really doubt they would ever use the steel inserts. Their attitude is that for the majority of the BSA fathers, their drilling block would probably only be used a dozen times over 3 or 4 years. That's "planned obsolescence"! Good enough for short term BSA fathers, but never for anyone that does Pro Pinewood Racing, like NPWDRL. So if you find one for sale, be sure of the steel inserts.