That Perry pump (VP-30) doesn't need the engine to shake in order to pump fuel. It gets pulses from the engine via a pressure nipple. Those pulses work a diaphram back and forth to pump your fuel.

The VP-20 DOES need vibration or oscillation back and forth to pump. As Ed already said, the VP-20 would normally be used on a 4-stroke engine such as your .91 But, it needs to shake back and forth to pump fuel and if your firewall and motorbox is going to be that rigid, I think you might need to go ahead and trade them off for some VP-30 regulators.

Proptop has a good suggestion about looking into the Cline or IronBay regulators. They work pretty well. They work DARN well. Same or similar plumbing, but a much cleaner and more consitant result than a Perry IMO More reliable and trouble free. Tune it once really good and tweak it in just right on the low end. Then you forget about it and go fly.

My only issue with the Cline and IronBay regulators is that you have to have an engine thats broke in pretty good. Not a used engine, but you definetly don't want to hook up a Cline untill you get about a gallon of fuel through each of those OS .91 4-strokes. I run all my engines just a tiny bit fat for about 1 or 1.5 gallons. Even on the low end. Not slobbering, but just a tweak rich. I find that my ABC glow engines don't really like to be leaned out to the max on the low end untill they are solidly broken in.

Okay, so when you put a Cline on an engine--that engine better be good and solid. Trying to run the low end rich has caused me fits a couple times untill it finally hit me in the head and I figured out why they wouldn't run. The Cline is such a precision device--it is so finely tuned--that any amount of overly rich on the low end just causes them to flood the engine. You need to tweak that low end needle down to the knats --ya know-- and get it set as perfect as you can possibly get it. If you don't, you'll cuss a Cline for the rest of your life.

My glow engines don't seam to want to be leaned down that far on the low end untill they have passed a fair amount of fuel. So, I made the mistake a few years back when I first tried the Cline--I was hooking them up to brand new engines and was NOT happy with the results. It finally dawned on me and I ran the engines in a mule plane for a gallon to break them in. Took them out of the mule and mounted them up in my flyer. Set the Cline and it was all smiles after that.

Just passing on my experience. You can do it however you choose. [8D]

Here's a link to the Cline Regulator:
its such an obscure website, you'll never find it if you search on giggle or any other search engine
http://www.billsroom.com/pcfs/

And Ironbay:
http://www.ironbaymodelcompany.com/W...or%20Main.html

Good luck. Lets see some pics of the plane.