Some really good stuff in here. I flip a-lot! Perhaps 6-8 times a season. Before you get all excited and tell me I need to back off and run less Class V, consider that I rarely flip in Class V and frequently run meat lines in Class III-IV with big features and calmer water below. Most folks don't intentionally seek these features out since there is obviously a good chance of flipping, but I think it is a good way to go for practice. Certainly enables one to speak from experience on a thread like this if nothing else.
On re-flipping in general, a heavy gear boat will require multiple people (or pulley system/derig) to reflip no matter how much you weigh or how good you are. Simple physics limitation. This is best done in an eddy or by the side of the river (don't want to have multiple swimmers again!). To get the boat to the eddy towing and/or people on top of upside down boat paddling are best. Do not attempt to bump/push! It doesn't work!
On mid-current re-flip, Only do this with a light boat that 1 -2 people can flip. Get all swimmers out of the water before doing this! As it comes over keep ahold of the flip line so you are not separated. Beware of the river around/downstream.
Tag-lines and flip-lines are different. Tag-lines are the 1" x ~9' poly webbing coming from the bow and stern of each tube on a cat. They are not useful for re-flipping, but incredibly useful for a variety of other things. Watching your boat drift away after you were unexpectedly tossed? Grab the tag-line. Buddy catching you in a small eddy? Grab the tag-line. Towing a upside down or right side up boat? Tag-line. Quick tie off? Tag-line. I have never seen a raft use 'em but it could make sense on a light paddle boat or small oar rig. Some say entrapment hazard. I say more good than harm. The reason not to use tubular webbing is it bunches at the end over time. Sure, it's strong, but it creates more of a hazard.
There are a bunch of different types of flip lines. I prefer ones that are pre-rigged to the boat rather than the waist wrap or cord in pfd pocket. This is primarily because it is difficult to get the cord off you waist or out of your pocket and onto the boat if the upside down boat (less stable with less to hang onto) is moving at all. All four types of pre-rigged flip-lines tend to work well:
- Simple strap: Like a tag line but at the middle of the boat. Simple and works, but has more potential to get caught around oar or paddle. On rafts these can be girth hitched onto the floor lacing. I run that on my light paddle raft and its great.
- Rope in bag: A bunch of places sell them and they work well. A bit of a pain to get the rope out of the bag, especially if it is tied on your frame (underwater after flip).
- Bungee Flip Line: Cats mostly, although could work next to the floor lacing on raft. Attaches fore and aft and stretches (bungee) to get good leverage for flip. Homebrew Bungee Flip Lines | Western Rafter. Stows out of the way nicely, but can limit the length/leverage so test with full rig. I run these on cat.
- Rope all the way under: Single strap attaches to frame on both sides and runs under boat. Nice for climbing on upside down boat. Be prepared to cut strap if you can't get the leverage you need while tied on both ends. Should be tight to avoid snagging. I think this has a larger snagging hazard than any of the other options and choose not to use it.