Amphibious Assult Buy Point Ratio (Hotseat)

[Shorebreak]

Hello all,

My friend and I have recently been playing a few amphibious assault battles on 90x110 sized maps; however, the attacker never seems to have enough to break through in any significant fashion, as there seems not to be enough artillery to punch through. We have been using a buy point ratio of 2:1 for the attacker. Does anyone have any suggestions on how to even up the flow of battle? Maybe a larger attacker advantage or larger map size? Thanks for the help.