this is the stiff part of a hinged stuff rig, it's not the one for a bag will sit far too high I think, if you want to use a pop up in a bag I would still keep it simple and just add some shot to a simple rig and check the presentation and that it doesn't sit too high above, which is why I like a wafter as it looks like a part of the mix not a beacon on top of it,
my thoughts on bags are that all Ingredients can be sucked in together at once, then hopefully the hook sticks In the lip as it lifts off, I don't think you need a complicated rig in a bag as the surrounding bait is all part of the appeal,
I don't think 2.5oz is a deal breaker tbh just make sure your hooks are sharp,