Somebody went to a lot of work setting that up. Tires on the ground a couple buddies and an engine hoist on the bow hook worked pretty well for me. I've seen some other people do it inside the garage with a hoist hanging from the rafters and an engine hoist on the bow eye... Usually took a total of 30min - an hour if you include rounding up a couple helpers.
I used 2 cherry pickers to do mine one strap around the bowl, one through the bow eye. I flipped it over without help and problems the second time. Just remember to to be SURE the strap cant come loose.
"The Constitution only gives people the right to pursue happiness. You have to catch it yourself ." - BENJAMIN FRANKLIN.
I have only been part of one boat flipping but with a half dozen or so dudes it seemed pretty simple. If i didnt have no freinds i would go find some vato's and get it done.... unless i did it alot i would not build something to do it.
on mine i used the tires/grass and ton of people way of doing it. On the one i just did I sandwhiched the transom with 2 2x6 (1 inside and 1 outside) and bolted them together through every existing hole i could find on the transom. dead center i through bolted a eye hook with large washers on both sides and left it just slightly loose so it would spin. hooked a engine hoist on both ends and was able to flip it both directions by myself very easily without every pulling it out of the garage.
pretty much similar to whats is showen just i used to hoist. advantage to the way i did was i could pull the trailer in all the way to one wall hook it up and pull both hoist towards the other side and pull the trailer out before flipping it.