I have been away from the Haven for quite some time (school, work, real life). I usually like to backseat moderate a bit (not to incur punishment onto those that do annoying things, but to steer them in the right direction and explain what is right and what is wrong). Usually explaining how things go here makes better members out of people. I hope this doesn't anger any of the moderators, but some small offenses usually don't warrant a suspension or even an adminstrator stepping in (but a friendly and curteous kick in the ass from somebody else can usually help).
I should be back on and browsing the forums more frequently in a few weeks after this semester is over, and hopefully we can help guide some of the newer members towards our much-loved NerfHaven etiquette.
The worst thing about Biofuels is that we aren't gaining anything from producing it! The costs of fuel to actually grow and produce biofuel completely negates any gains in fuel from using it as an additive.
Instead of gluing the back piece of the stock on and not being able to experiment with springs, you could put 3-4 screws around the circumference to hold in place. When you want to swtich springs, you unscrew it and it should slide out. Pop a new spring in, and screw it back up.
Carbon uses a similar method to keep his SNAPs together.
EDIT: Also, your screws don't have to go very deep, so you don't have to worry about the screws affecting the spring. Great mod, by the way! I have yet to buy the Recon, so I can't say much about the mod itself.