You KGB bag is as follows
1 fill as u mention from the transom. There is a check valve on this line and all the other fill lines as well.
1 drain as u mention starboard side
1 vent overflow on the port side
The second hole on the starboard side is for the bilge pump.
If you pop the fill pump cartridge out( move the black tab, twist and pop up.) it will have a tag for the gph. The factory was originally 500gph. You can purchase the cartridge motor itself for around 30 bucks (iirc ) and up it to 1000 or 1100gph for the best fill rate.
You can also lift the floor section up without unbolting anything and access all the hoses and routing. You just lift the floor up by the plug access port. Keep it as flat n level as possible and wiggle it forward. Viola instant access to everything.
CURRENT: 2008 SANTE 210
2000 Mastercraft Xstar
2004,2005 Ski Centurion Avalanche C4
2003, Ski Centurion Cyclone
99,2000,2001, 2002 Ski Centurion Elite V/Hurricane/lightning
88 2001 Nautique