Just went downstairs and hand-flexed a 160 Proto CTX and a 156 Infinity.
Not much difference.
That is extremely helpful, I would imagine a proto might be slightly softer than the infinity if it were of the same size, which is exactly what I am looking for. Its also a true twin which is what I was looking for and the 152 in only half a cm wider than the 151 infinity, so I should be able to ride it easily. I can't stop flip-flopping but I think I am leaning more towards the proto 152 now haha