Links? Hah! With my level of computer illiteracy, I'm doing well when I manage to post my own comments. I first read about this on the Rimfire Central website, where a 10/22 owner did it to stiffen the Hogue on his rifle with good results. I did one on my first SPS and was happy with the improvement, considering that it costs almost nothing to do. You basically cut slots in the crossribs inside the fore-end, allowing you to lay a couple of arrow shafts in there, reaching from just in front of the receiver to the end of the forearm. Make sure they don't touch the barrel, then glop in bedding compound to hold them in place and fill the gaps. It's a good idea to create undercut notches in the ribs to create a mechanical lock instead of just trusting the compound to adhere to the plastic. After it cures, sand it down to float the barrel and you're done. Not a lot of added weight, but very noticeable improvement in rigidity.
I know other guys on here have done something similar...maybe someone else can post pictures?