No biggie.
I only get the no Flow error if I forget to fill my 5 gallon bucket and the pump starts sucking air into the line. Then I just purge the tubing and unplug/replug the power and it's fine. I was just surprized that it was still "sensing" to some extent after the mod. As you said, it works great nearly all the time except for that instance.
I agree about using pumpsets. I actually got mine from reefdosingpumps.com and it's much better than the original tubing I was using. I couldn't hardly overcome any head with the regular silicone tubing because it wasn't pliable enough IMO. It wasn't sealing enough to pump adequately. I think I'll just pony up for the replacement tubing they sell for $5 for 2' becuase I know it'll work without the hassle (or at least until I find a confirmed tubing that works just as well).
I guess I'm always trying to make something better! :P