When you say 'full length' what do you mean? Scale length is the distance from nut to bridge - regular electrics typically run 24 3/4" (Gibson)to 25 1/2"(Fender), but there are huge variations from tenor to baritone and beyond at both ends.
If you want an open tuning on this sort of scale length, I'd suggest trying something like 024 W, 016 plain and 014 plain from bottom to top, tuning it GBD low to high and seeing how you get on....but it's just a suggestion..there's no rules...whatever sounds good to you.
Like Kenny, I like to keep it simple.I tend to go with the 3rd,4th,5th strings and tune to high "G" "D", and LOW "G" . Later after you get your feel for the instrument then I'd start trying different tunings and or strings.