sadsack,
I have used acraglas often and it is a good product.
I don't know much about Sakos synthetic stocks but do know that acraglas does not bond well with some synthetics.
Even if it does bond well with the OPs stock, I know for sure that you can not just pore or smear it on a crack and have a repair....you would at least have to take a dremel and carbide burr to the crack and widen it and make it deeper adding a few areas at proper angles to aid in mechanical adhesion.
I was assuming that Sako would not need the complete rifle ( could be wrong) and would just need to see the stock. If so, sending in a 2lb. stock wouldn't be that expensive.
If they look at the stock and see no signs of unusual abuse, I bet they would send him a new one.