Taken a little while back but I've decided to revisit this data to see if I can extract a bit more resolution out of it. Went and stacked 320x120s subs and not just the best 146x120s which had FWHM below 1.8". The difference? Not much.
Not only did doubling the exposure time not make much difference to the background smoothness but it also didn't change the FWHM much either. This is possibly due to the weighting I've used for stacking but it was an interesting test to run.
Link to Astrobin
In the centre the stack it had a FWHM of 1.65" so seeing has been pretty kind. Actually has me considering an AO-X to potentially help eek out a little lower FWHM on the nights of better seeing. Going completely unguided at the moment which has its benefits (never chasing the seeing with guiding) but there is some slow (0.1-1s) atmospheric movements which can potentially be removed with an AO unit.