Thanks for all the replies! I'm somewhat glad to hear I'm not the only one. I thought about it being the fit, because it is slightly long, but if I went down a size then it wouldn't fit her giant shoulder and withers. Plus, I've seen her urinating where the urine hits the strap and splashes all over her.
Last night was the first night with the baling twine. It was an improvement, some splash but not much. I think in the off season I will take the blankets in and have leg straps put on.
Just be sure you buy fully elastic leg straps, not nylon ones with partially elastic ends. If your horse slips in the field the nylon ones will slice right through their leg whereas the fully elastic ones will give and not cause a nasty gash. Ask me how I know
My mare also has the Amigo XL (wide shoulders) and the butt strap. I have also noticed the splashing on the strap and down her left leg (never the right!). I wash the strap every time and since I have the rain sheet also, I switch them around. I will look for the elastic under the flap. Otherwise, I love the blanket without the leg straps. My mare is older and mature so does not play around in the field.
My daughter's gelding has the same blanket. He is young, plays around but the lack of leg straps has not been a problem.
I feel your pain - I do a lot of ass scrubbing during blanket season! I too have all Rambo blankets.
At this point I have just accepted it as part of the disgustingness that comes with having a mare that I keep blanketed.
Of course, my mare is probably the dirtiest animal I have ever met! It wouldn't matter if I switched to leg straps though - she has super powers when it comes to smearing pee and poo on herself. Oh yeah, and she's gray.
ETA: I do use the strap that is sewn in to the tail flap, but I've never had the tail actually stay there.
This is why I won't buy a blanket without leg straps. I've never been happy with any blanket that didn't have them. I also like fleece at the withers and shoulder gussets and Rambos don't have those either. I guess I'm the one of the very few who really can't stand Rambos.
The Rambo we have, have a sort of loop under the edge of the flap. I run the tail cord through it, on the theory that when the tail is raised, so is the flap, which will keep the tail cord flush against the underside of the tail. It does seem to help a bit, but not completely. Having seen blankets blown up so that the rump is completely bare makes me cautious about leaving it off completely.
This, if you have a tail cord. If I don't use the cord, my mare splashes herself.
One of my amigo sheets does not and my mare sometimes has this issue.