RE: Numbers for ST G21/35 DDD head
The K&B 4011 has a baffle piston, as do all the K&B 40s. The metric elephant engines are all ABC and Schnuerle ported. I ran the 5.8 (= 35) a lot in control line slow rat. At the moment there is Quickie Rat, which is dominated by the 4011. There are various rules to keep things simple, and the venturi size is restricted when speeds get up to 110 MPH, I think it is.