New to Helix, and I use it also for acoustic.
I'm heavily underwhelmed by IRs as well, unfortunately: I downloaded all the Mama Bear ones and Aura ones, loaded in Helix and tried them all: they all have a strange and annoying (and unremovable) resonance in the mids. the only way I can use some of them is to blend them very very low (15% maximum, 10% for 12 strings).
I've had better results with para eq (slight boost at 100hz, heavy cut at 905 or 1200, slight boost between 4k and 10k).
For reference, piezos in my acoustics are both Fishman SOB (only piezo portion used).
Yet to try 3 Sigma ones...