Personally is stick with the mid and try and find a setup for a track you race at from the website below. After a few weeks of driving mid if you go back to rear you will realise how much less corner speed a rear car carries and the mid can b faster in low grip due to the amount of steering they generate
http://www.petitrc.com/setup/schumac...CougarSV2.html
Currently I can't recall the last time I sawa rear car run competitvly - last year I ran a hybrid front motor car and it was as fast if not faster even on blown out grass over most mids so that sort of defied convention lol
I was never a fan of schumacher cars (fiddly and over complicated IMO although there's no doubt the Kf is fast) and if you are still thinking about having rear and mid options you'd be better off picking up a used yokomo bmax 2 kit that can be swapped from rear to mid in about 30 mins if required, durability on this car is very good and they are popular at many tracks also.