I hated the mixes when I tried it… bag got lighter, but also more unpredictable, and would sometimes settle wonky or shift unexpectedly.
Since then I’ve ended up just carrying/using two totally different bags…
I use a Plus1Plus1 with all the heavy sand it came with for most props and positions (first/only time I’ve got a sand-filled bag where I didn’t empty any sand out, the Plus1 broke in fast because it’s so heavy and loosened up before I needed to take any out), it’s heavy, near 11lbs.
I also carry/use a poly-filled Wiebad Mini Range Cube which is ~5lbs and far more squishy… it’s my prone/modified-prone bag and is a better size/shape for that IMHO. While less rigid/solid than a sand-filled bag I find it a lot faster for me for that stuff.
They’re nothing alike, but either are great at their specific jobs and both bags work together well if I have to stack them for some reason.
Point is: 2 might be better than 1, YMMV, worth a try.