Okay, I finally went and built a spring compressor similar to this one -
http://www.network54.com/Forum/79574/thread/1257146873/FS-++Spring+Compressor I had been using a simple bar clamp with a split fixed end that formed a 'V' and installed a board with a hole in it for the barrel. Although it worked for my airguns, I recently has a chance to work on an FWB airgun and let's just say my bar clamp spring compressor just barely fit the bill. You see, the FWB safety switch covers a quarter of the back end of the trigger assembly and I wasn't able to get the compressor foot squarely over it. I had to hold the compressor foot in place while disassembling and reassembling so it didn't slip off. Okay, lesson learned and I'm not one to never admit when I'm wrong, and I was wrong for not building one in the first place.
I went out and built 2 of these spring compressors and actually gave one to my favorite local airgun shop, because that's where I got the idea to use a bar clamp and that's what they were using. So now, I have a tool with which to safely disassemble an airgun, as do my local shop.
Here's a picture of the one I built. I used a 2x8 base instead of a 2x6. The 2x4 wood blocks are reinforced with 2-1/2" screws (predrilled so the wood didn't split) - sort of like rebars in concrete - when pressure was applied (this is where my training as an architect came in handy).