well, I tried my system out this weekend. I tee'd into my main line already for stock ballast. I tried filling both port side(stock and custom sac) up at the same time, and the fly high bag wasnt' filling up. what's going on. I upgraded the fill line from 3/4 to 2" line. thought it should fill both up fairly easy. come to find out i have to fill separately. my 750 pd bag fills faster than my stock 350 pd bag. tsunami pumps work AWESEME. prob 3-4 minutes and she's full. I did run a vent line with check valve to empty line and it seemed to work. I got a couple more through hull empty spigots(i think that's what they are called) that i'm going to drill through and just run a totally separate line for venting. now that i've drille two holes through, it's not as bad as i though. thanx for all the info and help boys. I'll try and get some pics.
i had to leave the boat at dealer, getting trailer surge breaks looked at, not working. did i mention i hate surge breaks. I would have ordered electric had i known. my rant over.lol