I think that's a good decision
I've fired G3 and HK91 rifles with both fixed and telescoping stocks. I was about to buy an A3 stock for my HK91 at one time. My fixed stock 91 was extremely accurate, fired from a solid rest or a bipod. With good ammo, first round hits at 350 yards were entirely feasible - - fartherest I tried it.
I was disappointed to learn that the A3 stock was so uncomfortable. I really wanted to like it, but I had a lot of trouble getting a good cheek weld on it. I even tried putting a folded blanket over the stock for padding, and this was only a slight improvement. Yes, I could make good silhouette hits at 200 yards, but that wass about it.
I shot a friend's G3 for several magazines, interchanging the A3 stock and the fixed stock. With the fixed stock, in semiauto, I could shoot it almost as well as my own 91, and did pretty well in full auto. Using the A3 stock in full auto, it was actually kind of painful. Even at 100 yards, it was only good for area fire.
I was fairly experienced (for a civilian) in shooting rifle-caliber automatic rifles, and I am really not very recoil sensitive. The only other automatic rifle that ever hurt me as bad was an AR10 - - very vigorous in semiauto fire but nearly unmanageable in full auto from the shoulder. Curiously, though, I could shoot both the G3A3 and the AR10 pretty well using an underarm position, at 15 -- 20 yards. I felt this was only a stunt, because I'm a big believer in aimed fire.
Best of luck to you.