I finally got it! I didn't necessarily get points for style, but I made it! I did juggle a little, but not much. I juggled the last 2 groups of bosses just because I could, though one got through. The key (for me) was slowing down the Spawn Boss while sending the Flyers immediately after the Spawn Boss emerged.
Didn't even get close to killing the Flyer Boss, though, and that was with 3 maxed out Squirt Towers, 1 Squirt Tower that was in its dormant-stage building to max level until the Flyers were maybe just past the half way mark, 1 maxed out Swarm Tower, 1 level 5 Swarm Tower, 2 maxed out Frost Towers and 1 level 5 Frost Tower.
Most of my life-loss were from the Spawns fairly early in the game, iirc.
Thanks for the advice qwints! I wished I had seen it beforehand! lol! BTW, what are snap towers?