Are you looking at purchasing an 11" Kostov SepEx or do you have an 11" Kostov and you think its SepEx? I have two 11" Kostov Series Motors with interpoles and neither are SepEx. They could be used for Regen if a controller was available without having to deal with over seas and very slow companies. Your actually better off without the regen as you really don't need it. It would be good for helping stop the vehicle but with good disk brakes you'd be better off. The cost and complexity of doing regen on a series motor along with the fact that only one company really builds a controller that will allow regen with a series motor with interpoles. Not the best in terms of needing good close at hand customer support and availability of reasonable priced parts. A 9" would more than likely suit your needs just fine with a good series motor controller. Don't mess with dual controllers to try to make a SepEx run. If you must go sepex you can use the Kelly Controller but the controller is not a super high end one and will give marginal performance. Yes it will do regen but your better off with a good controller and a good series motor instead. I have been on the same page as you with regen with DC but after driving my 9" motor in my Ghia you really do not need regen. Really.