I'm looking for a low volume but fairly stiff/rigid insole to put in some rubber hunting boots.
Right now I'm using an older model of Superfeet black/carbon but would like more support
All of the Superfeet are low volume and stiff. You might try the orange? I'm sure superfeet likely has a website with descriptions of each color? All of the superfeet are too hard for my feet. I prefer a lot more padding. Unfortunately most padded insoles have more volume and aren't stiff. I buy boots that are around 1 to 1 1/2 size larger so I can add thicker insoles and vary my socks (thin or thicker) depending upon the weather. It's possible to cinch down the boots tight when using lighter and loosen them up for thicker socks. Maybe the orange will work for your particular feet?
I can't seem to find the source, but I've read somewhere that Superfeet are supposed to have very little cushion. Instead Superfeet shape your foot to provide natural cushioning.
That's why the heel of Superfeet insoles cup and hold your heel instead of letting your heel splay out.
I can see how a harder insole with the correct form will keep your feet more secure. Superfeet orange may be a good option....you might give them a try? Everyone's feet are a little different. I don't have problems with my heels splaying. If hunting on hard surfaces my feet take a pounding without adequate padding....especially on the balls of my feet.