Rear ballast bags for Sanger v210

I'm going to order some rear ballast for my 2004 Sanger v210. I was wondering if anyone knew what the dimensions of the storage areas are (on either side of the engine). I've read on a number of old threads that people don't put all that much weight in the back of these boats. Should I get the dual 400LB bags or the dual 750s? We always wakeboard but if we could get the wake right I'd love to try surfing some day.

My boat has the factory front ballast with a thru-hull right in the ski locker and a drain/vent coming out the side of the boat. When I add the rear bags, I guess I have to put another thru-hull in the back right? And then get a T to fill both from one hole or should I drill two holes? Then the vents/drains need another thru-hull on each side?

I'm not sure whether I'm going to go with a reversible pump or a set of aerator pumps. For this season I think I'm just going to throw the bags back there and fill them with non-permanent pumps but I'll integrate it next season when I have more money and storage on-site.