Does anybody know of a good quality bipod that is lightweight? How do you connect a bipod to a stock Colt 20" rifle? Do you have to change the handguards to get one with a place to screw in the bipod? Thanks

Harris calls theirs "super light" or "ultra light weight" but I don't know how they compare to the Versa-Pod for weight.

Harris bipods attach to a QR sling stud.  If you have regular A2 handguards you can get an adapter that fits through the hole in the HGs and provides the stud.  It's basically a threaded stud with two special washers to fit the shape of the HGs.  Just installed one on mine, but haven't been to the range yet.  Paid $10.99+tax at the local gun shop.  I'm sure places like Bronells have them too.

Have you checked out the ARMS bipod?  It's very compact and minimal bulk as opposed to the others.