Just finished a project with a contender G2. The rifle shoots much better than me. I have seen some better groups as my bench technique improves. The only problem I can see is the rifle is so light that the smallest presure on the stock changes point of impact. Can i fill the open space of the forend or butt to add weight? The stock/forend are synthetic and I hate to ruin them with hot lead or? please help

You can use lead shot, then pour epoxy over it. That allows you to measure a specific weight of shot to give you the balance or weight gain that you want. Epoxy generally won't stick very well to a plastic stock. You have to rough it up or drill locking holes to give the epoxy a good mechanical grip.

+1 on the lead / epoxy mix. but I mixed the epoxy with the pellets and then poured it into the void but beware them little lead balls with epoxy slime on them do strange things if you let them wander off the work site. I was working on a stock and looked down to see three of the pellets slowly rolling down the vertical side of my work bench like they were sneaking off and leaving a trail of epoxy as they went...

If you just want to firm it up and add a small amount of weight just fill the voids with spray can insulating foam then use acra glass bedding over the top of the foam. This adds a surprisingly rigid feel to the stock and it sounds better as well because you filled the hollow voids and you are only adding the weight of the acra glass bedding material. If you think you want more weight than that add a little shot in the void then spray the foam over it and conplete with the acra glass.