Light carbine bench technique

I have a Ruger 77/357 stainless/synthetic that keeps climbing out of my 15" BullsBag (the one that has the Tuff-Tec synthetic material, not suede; filled with sand). I use a reflex sight on it, so I can't use my left hand to press down on the front scope ring (unless I put the scope back on, which is no trouble to do). I switched to ear plugs from muffs so as to reduce side pressure on the cheekpiece, which seemed to help some. The forend is completely surrounded by the bag wings, so I can't grip it. I've put soft deerskin and carpet pad material between the bag and the forend, but that doesn't seem to make the bag hold the forend better.

The only other rifle I've used with the BullsBag is my CZ 452 American .22LR. The bag seems to grip the walnut stock very well and I can get wonderful groups with it when I do my part.

I get 1 1/2" - 2" groups at 100 yards with factory ammunition (holding the forend in my left hand supported by a regular sandbag, with a rabbit ear rear bag). I think it will do better, judging from the number of times I get two shots touching. If I need to use something other than the BullsBag, or can do something else to improve my technique, I will. Thanks!