After using Pumabuild a lot and having experience of shawspeed, I know that John @Shawspeed knows far more about the sigma engines than Alan does.

Alan Farmer is a recovery truck driver who spotted a niche, took a risk on setting up a business and it paid off, fair play, but he's not a talented engineer IMO, heis someone who learns on the job. Some of the bespoke work i've seen from there has been pretty 'industrial' to describe it politely.
Although I will say the work I had done was always decent although it was just routine stuff

John @shawspeed knows these engines better than anybody IME