Question on deployment zones for a narrow table

I'm new to the game (watched all the ianmtanding stuff and have a few games in on TTS). I've just about got 2x 1k point forces printed/painted up and I'm ready to convince/trick my friends to play with me.

The table in my game room is only 3'6" wide, I'm trying to figure out if I should make little extensions for it to fit a 6x4 mat, or if I could just go with a 6x3 mat

With less depth to the battlefield, is it more important to maintain the 80cm between frontlines during deployment, or to allow 20cm for deployment area depth? I don't know which (if either) is disruptive to the game or messes with any assumptions about what can/can't be in range until turn 2.