Clean bulk cycle

Hello,
What would be reasonable dose of deca for a slow bulk while on TRT dose of test(200mg/wk)?
I'm currently finishing my cut at 200lbs with ~10% bf and thinking about doing 20wk cycle with deca, starting around september.
I don't want to just up the test dosage since current dosing is A.I free and without any sides so I don't want to mess it up(and my hairline).
Is 400mg/wk worth trying? I'm thinking about 2-3lbs of weight gain per month.
Haven't using anything except TRT dosage of test and tbol.