Batteries Groups

[Atango]

Hello.

I purchased a sailboat with 5 house batteries and 1 start battery. The battery banks are separated with a switch.
Right now the house bank is 2 X 27 group lead acid, 1 x 24 group lead acid and 2 x 6 volt lead acid (golf cart).
My question is I would like to replace all the house batteries before I leave for a long trip. Should I go with all group 24 (5) batteries or 3 group 24 and 2 group 27?
I don't have room for more then 2 group 27 batteries. Is there any problems when you mix group 24 and group 27 in the same bank?