Octograb on older Taz?

I have a kittaz that has been upgraded with an aerostruder extruder, everything that makes it equivalent to a 5 and all X and Z parts of the 6. I have been looking into a flex plate bed and have questions. The store says the octograb kit is for 6 and newer only with the modular bed. The modular bed is for any 24v Taz 3-6. So why won’t the octograb work with 3 through 5 if I add the modular bed? The only change I see needed is to print the new corner blocks and change to washers or low profile corner tabs. What else am I missing?

The reason the flex plate is not technically compatible is the corners on the Taz 5 and earlier stick out into the build area too far for the plate to sit flat.
Granted, you could modify the corners or the plate itself to allow it to fit, but that is the reason for the incompatibility.