Sheppy, welcome to the forum. IMO, the best use of the evolve is in the hybrid mode (along with easy pedaling) where you can achieve some excellent range. In the single kayaks that means it has to use the rudder mount. The evolve rudder works great when on, but when not running, would only provide marginal control on the Oasis in the ocean with higher demands from wind and chop. So a tandem application is really the best of both worlds with maximum rudder authority from the large Hobie rudder at all times' and hybrid power (evolve in the front well, fins in the rear well) available at all times.
The whole package weighs only about 15 lb. If you went with the rudder mount, you would put the battery (about half the weight) forward. The 7 or 8 lb. motor wouldn't have any significant weight effect on the stern. On the other hand, with a front drivewell mount you should be running with ballast in the bow to keep the evolve from occasionally sucking air in the ocean chop. Whenever soloing the Oasis though, ballast improves handling and performance, regardless. Under that circumstance the evolve should work very well in the front drivewell.
All that said, I have several hours with the evolve with both drivewell and rudder mount with various combinations of motor, pedals and sail; I have lots of solo time in the Oasis, but I have never tried the evolve on a tandem. I think it would be the perfect application though. If you try it, be sure and keep us posted!
