the original RFR guts looked like this (note: I sawed off the barrel previously)

I hooked up the new airtank where the old spring and plunger used to be (ignore the trigger/valve mechanism on the left of the red goo-meter - I ended up changing that; see the next pic)

To fit the airtank in. I had to do some considerable hacking/sanding of the existing plunger/spring frame. I seriously need to invest in a Dremel kit.

On the other half of the rifle chassis, I drilled a hole to allow the "liquitron" goo meter protrude. Yeah I kept the goo, partly cause I was too lazy to reroute the airlines and partly for effect. I also drilled a hole for the airhose (between aritank and pump).

I also cut down the white plastic arm (that connected the lever to the spring) so as not to interfere with the airtank. To allow the shell-ejecting mechanism to work, I glued a small piece of plastic to extend the orange ejection trigger - this allows the sawed down lever arm to trip the ejection trigger. Thus, the lever/clip feeding system works as usual. (sorry - no pic)
After experimenting on a few different valve-trigger mechanisms, I settled on a low tech but reliable solution - steel wire (for hanging picture frames). I secure this to the end of the valve pin. Notice there's also an orange piece (scrap from amodded NF) glued to the airtank to support it against the old spring frame.

I drilled a hole in the existing RFR finger trigger to secure the other end of the wire

After ALOT of trial and error and troubleshooting, I put it back together. Assembled it looks like this.

I still haven't mounted the pump. I'll probably keep it (horizontally) on the right side of the blaster so I can cock the lever and pump with the same hand. I'll probably also change the pump handle.
Cosmetically the fit wasn't perfect as even after cutting out some space for the protruding airline, the airtank causes a bit of a bulge in the chassis and from above you can see a gap (even when the screws are tightened) - oh well.

Now for ranges:
After about 3 1/2 full pumps, it gets about 45-50 feet (stock darts). That's only about 10 feet more than the stock(springer) version with the same dart/shell. I figure, I can get even better range with an extra pump or two (I plugged the over-pressure release valve) but I'm a still little of a wuss when it comes to pumping the gun. After spending 2 days modding this thing, I didn't want to immediately bust the airtank.
In any case, the integration was moderately successful, it gets slightly better range than the stock RFR and is considerably quieter. It hasn't lost its clip-loading capability though its RoF is obviously a little lower because of the pumping. When I get around to it, I'll work on the pump handle and give it a new paintjob.
Again, I'm a nerf noob and this is my first attempt at an integration but I hope it gives you guys some ideas (maybe of what not to do
