That's the aspect of the OS .91 pump that is really important to me too. They are one of those engines that rarely if ever deadstick.

Mine's mounted inverted. The trick to handstarting these engines when they're inverted is to use a tee junction between the pump and the clunk for fueling. Set the throttle to full when you fuel up. The pressure of fueling forces a little fuel past the pump/reg and into the carb - just enough to prime the engine for a backflip. I just flick the spinner clockwise and up she lights!

There are another couple of advantages to the pump engine:

1) You are not compromising your state of tune. Rather than tuning for peak then richening back a few hundred rpm for reliability, with the pump you just tune for peak, then back off slightly until smoke output slightly increases. RPM drop is minimal, and she'll hold that tune for at least the rest of the day, if not for weeks or until the climate changes significantly.
2) because you don't need exhaust pressure on the pumper, you can fit the EX503 straight pipe to the engine. It makes a very quiet engine only slightly louder yet adds 200-300 rpm. That's a significant increase and it only gets better once the model is airborne and the engine unloads. With the free flowing header, it seems to run cooler too

The OS .91s I've seen without the pump have also been good runners.