When you put them in front of the tank, you are moving that weight forward. In my case, it hurt top end....took a little more trim to get the boat running clean. That may not be the case if you've removed the pad lip, as it should have more bow lift with the lip gone anyway. With the lip, you have more stern lift so it should carry the rearward weight better. I didn't like the way mine drove with the batts in front of the gas tank, so I moved them back to the wingtips after a couple of trips. I've ran my boat with several setups:
1) a wet cell group 27 in each wingtip
2) 2 optimas in front of the gas tank
3) 2 optimas in front of the gas tank and a cranking battery in the left compartment
4) 2 optimas in the left compartment adn a cranking battery in the right compartment
#4 is actually my favorite configuration. the 2 optimas plus the cranking batt together weigh almost exactly what the 2 group 27s weighed, but i have a little more weight on the left side at rest which balances out perfectly on the top end.
