I'm wondering if PilotDAR knows full well what the Mach loop is, and that's beautiful irony, or (entirely fairly) has no idea
Sidenote - the mach(ynlleth) loop is a locally well known low fly practise route for the military folks. Usually the faster pointier flavours of military folks at that.
I also like the idea of doing it.. BUT in order to 'do it' you'd have to be breaking low fly rules, and probably quite a bit of common sense. Not to mention that the ground climbs pretty steeply in a few spots. Tooling round at sensible/legal alts would seem a bit futile. Much as I'd love to play fast jet for a day, IMHO I'd leave it. The consequences of meeting one of the more usual denizens don't bear thinking about, even if it's only a near miss.
I wonder what the response from valley etc would be!