I run my piped and high timed Webra 50 with a backplate pressure tap and it works perfectly...so I'm not entirely sure if there is any hard fast rules. My other post was mostly about strong advice I got from the Nelson gurus...but my Webra contradicts their advice. It doesn't put out nearly as much power as a FAI pylon engine though. I'd prefer to tap the backplate and try that before punching a hole in a perfectly good pipe.