I've got a nice matched team of full sister Percherons. Been putting up with this problem for quite some time. One mare starts out faster than the other and after a few miles ends up slower than her teammate. The other mare goes a constant speed all day long. A 20 mile day she stills walks along at a nice clip. They get seriously out of alignment. I've put chains on the double tree to prevent sheer but of course is not an answer for the alignment. Short of a buck back strap, ( I'd rather not slow down the consistent horse ) or replacing one of the horses, any ideas? Pulling small people mover and horses get a break every 4 or 5 miles. Thanks.