I've used the MP10 w/ foam, but I wouldn't recommend them. If you don't crank them up past half speed, you MIGHT be OK. I've seen horses get stuck to the foam because the suction was too great when they get too close to them. I had it on reef crest mode at full steam and before I could peel the horse off the vortec, the flow decreased and released the horse, but he wasn't too happy about it.
Otherwise, the horses seemed to love the broad gentle undertow from it. They would often swim in the current like a treadmill (swim into the current, but go nowhere).
Scott