Nice image David. Photometry could be useful. Do you plan to submit it to David Bishop’s website? there are no measurements or images for this SNe there yet.
Only clouds and bands of rain on this side of the country tonight unfortunately.
I suspect it is close to maximum now and since it is a type 1a I had a go at estimating how bright it should get to at maximum.
According to NED http://ned.ipac.caltech.edu there are no redshift independent distance measurements for ngc4964 but based on the redshift the distance would be ~36Mpc. (Though for a relatively nearby target like this the errors could be high)
Using 36Mpc and an absolute V mag of -19.3 at maximum for type 1a SNe gives an apparent V mag at maximum of ~13.5 (not taking into account any extinction) so your mag 14 guestimate seems reasonable.