Ideally you can have lots of 21/31 2x2 plots to just crossbreed new seedbags, which would be safer as they are guaranteed to not go over 23 growth (and your crops stats would always be near perfect).
I might try the 2x2 plots (with water at the center of each group of 4 such plots?) in my next game, but since I already had 9x9 fields (with water at the center of each), I split each of them into four 4x4 fields.
Although, I'm used to crossbreed and spread fields on the go (while always scanning them and destroying any growth >21 crop).
That gets frustrating when 40% of the crops produced by crossbreeding will be outside the target 19-21 growth range (and therefore need to be destroyed), and I think a mistake while doing that was what cost me half my aurelia crops yesterday, though I couldn't figure out what happened to the rogue crop.
This can be done at the very early stage too since the scanner doesnt need the crop to be mature as you probably know.
I think the IC2 Cropnalyzer has had some changes recently, so it might not need that either now.
P.S. I'm curious: do you use default textures or a resource pack for your crops? With default textures, it's hard for me to see the difference between the last two stages of coppon, and with Soartex textures, it's hard for me to see the difference between the last two stages of stickreed, so I've been using Sphax 64x textures for the IC2 crops and the 32x textures by IChrisI that I adapted to 1.7.10 for some of the GT crops.