Well done.
I took images of SN2013E on 7th through BVRI filters 3 days after discovery. Its measuremenmts were
mag B = 14.77 V = 14.59 R = 14.37 I = 14.32
This is pretty close to your estimates. Very good.
see
http://i566.photobucket.com/albums/s...ps2e0bb9a8.jpg