Why is the Sumo bow sack so much better? I just got the fly high as a gift for Christmas and now wondering if I should sell it and get the sumo?[/quote]
A couple reasons. As stated above, the shape of the mushroom is a little different and seems to fill the voids a bit better, then the stem part is longer. Both those things allow the sack to hold a bit more water. When I switched to the Sumo bow sack I was able to pull out 200 lbs of lead in the very tips of the bow and move them back to under the driver kick panel and next to the batteries, this gave me the same stance in the water when weighted, but allowed my bow to not be so low when ballast was drained. I am only guessing, but I think the sumo holds around 100-150 lbs more, just my observation though.
Another thing with the Sumo's is the ports are 1" inside diameter, and if you have a 2014 Axis or newer, they all use 1" I.D. hoses and high flow pumps. It is ridiculous how fast the sacks drain in the 14's as opposed to my 2011. You have the 2014 so Sumo matches up perfectly. Another reason is the placement of the ports on the sack. The Fly highs have one fill/vent port in a good spot, farthest back of the two, and is accessible from under the chillax seats. But the second fill/vent port, farthest forward, ends up under the bow floor, pushed up against the fiberglass, and unaccessible once filled…. can't see if it is leaking, and it kinks the elbow, hose, and or sack at that spot. The Sumo's moved both fill/vent ports farther back on the stem of the sack and both of them are visible and accessible under the chillax seats. This also gives you a shorter run of hose from your fill pump or vent. The last thing is Sumo's have an additional port that is a manual fill valve for hand pumps that can be used to "burp" your bag. This spring loaded valve is positioned perfectly with the access hole under the center bow cushion. So you can burp your bag if you want/need too. Or if you have a pump failure, you can manually fill your sack very easily.
If you can, try to go with the Sumo's for all your plug n play sacks. They are perfect matches for 2013+ malibus and 2014+ Axis. They are less expensive too, at least the last time I checked months ago.
If not, the Fly Highs work just fine. I had the bow sack, but after seeing and trying out the Sumo bow sack, I ended up selling my Fly high to get the sumo. I plan on increasing on my ballast hose sizes to the 1" I.D. stuff and switching out my FH 750's in the rear to add the Sumo 600's. But that is down the line.
heres the thread on the bow sack comparison I did a while back
viewtopic.php?f=15&t=1563&hilit=sumo+bow+sack&start=20Page 3 has my write up and pictures. But that whole thread is a really really good read with a lot of good info.