I'm waiting for better pics from the rest of my group, but here is one of my cat (Jack's El Tigre 17'x28") with a bimini. The bimini is at a bit of a cant in the picture because I'd just unloaded gear at camp and randomly strapped the back of the bimini to my water cooler. (The other boat is a 156d Aire, which has the first bimini I installed and convinced me not to go back to using an umbrella.)
I removed the two rear straps and mounted one to the middle of the rear bow. That strap is connected to a river strap that allows me to cinch it tight to any number of points (gear pile, raft frame, water cooler, etc). Not having the two rear straps means that nothing interferes with pulling my oars in, and I only have to undo one strap (passengers undo the front two straps) to drop the bimini. Plus, I use the river strap to cinch it tight when it is down.
One complaint with my set-up is that I wish I'd bought an 8' 4-bow bimini as it would have provided more shade. However, it was a rush purchase for a looming trip and I wasn't sure the 8' would fit given my mounting area constraints. The rowing seat is not as shaded as I would like. I plan to get a sliding track, as mentioned in a post, above.
Another complaint, though minor, is that the tubes of the bimini can rub against the oars when they are pushed down to clear obstacles/waves. This is due to the bimini resting on my table, which is high to clear groover and rocket boxes stored on my floor. I can make the tubes sit lower if I "tweak" them into an off-set alignment, but similar to a mention above, my plan is to add about 9" behind my drybox (seat) and table for 2 extra rocket boxes and the bimini will then lie flat on my deck and not interfere with the oars at all.