I think you should be ok. I always see people checking in two large suitcases in economy. You can probably find more info here. Although it may not be clear if *A Silver will give you an additional bag allowance.

I have on occasion been over the bag limit, but they usually just let it slide. Although I can't tell if that is due to my frequent flier status or not.

What I might try to do, given your situation, would be to try and check in at the Biz class counter / S* counter. Hopefully the check-in staff would just let the two bags go without any issues.