There would seem to be only a few possible permutations of options available to you and I do not think there are any magic bullets for you... unfortunately.
I reckon the best answer will probably be to convert your Evolve to the drive-well mounted version (assuming that it is possible to do this) and to use the sailing rudder all the time; that way you will have the benefit of the Evolve motor and the better steering capabilities of the larger rudder.
Of course you may not want to do this because you have clearly already decided that the rudder-mounted Evolve is the best option for you but I think you may have hit a drawback of your chosen option in relation to wanting to sail as well.
In my experience of sailing Adventures the small rudder is really not up to the job when sailing the boat as it does not exert sufficient leverage on the boat to be able to counteract the force of the wind in the sail. Clearly the same may also be true of the rudder-mounted Evolve and in both these situations the most obvious solution, however unpalatable that might be, is to replace the rudder with a larger one.
Another thing that I think you might like to consider is the amount of drag that a propellor creates when sailing - it is considerable and the reason why many yachtsmen opt for folding propellors on their boats. I am no expert but it may well be that the drag of the propellor is as much to blame for the poor sailing performance of the Evolve rudder as is the small surface area.
I think you may find the drive-well mounted Evolve a better all-round solution because it will allow you to take the prop out of the water while sailing and I suspect that this will make a marked improvement to your sailing speed compared with having it permanently immersed which is the only option you currently have when sailing.
There is a noticeable improvement in the sailing performance of my Adventure when I have a drive-well plug in place rather than the Mirage drive - I attribute this to the additional drag of the fins being in/out of the water and I always replace the drive with a plug if I am going to spend a reasonably long period under sail (pushing one foot forward to fold the fins up helps but I still sail faster with a drive-well plug)
The Adventure is a better sailer than the Outback by quite a margin and I think you will find that the drag of the Evolve and its propellor is likely to be much greater than that of the Mirage drive fins - my recommendation to you would be to get the Evolve prop and the mirage drive fins out of the water and use a drive-well plug if you want to get the best performance out of your boat under sail.
As I said: no magic bullets I fear