Shimano 105 shifters with sram rim calipers

So, I mentioned in a previous thread I had given the Caad12 a makeover. I stuck some R7000 shifters on and run them with an older set of Sram red aeroglide calipers.

The braking on them is pretty poor. I had read beforehand that the pull ratios meant that compatibility was an issue, but I have run different brands of shifters which different rim brakes on many occasions and had no issues.

In essence, I have to the pull the brake really hard to stop, and have to grip the entire lever to get enough purchase. The front brake has 'softened' up a bit and is now useable but the rear is still terrible. When the bike is stationary if I spin the rear and brake, it grabs with no issue, but on the road with weight and inertia, the brake power is negligible. Any kind of modulation on either brake is also virtually non existent.

Any tips or tricks to remedy this, or is it a case of switching out the calipers to shimano 105 as well?