Well I am back guys.
1) it is very stable. flight video will be uploaded soon.
2) Tail is bit shaky. (I will strengthen it later)
3) yes you can put 2 motors under the wing. But as it is supposed to be a trainer so it has to be simple and safe. High center mounted motor in pusher configuration is safest in all aspects.
And here is my version of FT-Explorer, hope you like it.