Not sure if you bought but if you go hammerlock dont go too long or too wide try and keep them as close to the size of tanks if possible. You dont have to replace the board, just get some thick lino or contact and cover them before use.
I went and bought $180 unit, pallet racking. Got sick of the other stuff like hammerlock. It always worried me.
I bought the big $130 unit from officeworks for 2ft tanks... it sorta bowed in the middle.