Mine was tall enough that I could get under it to put antennae on the belly. I want to say that the part the spar area rested on was probably 14" or so. I also made it wide enough that I could use that part as a step up to then step over into the fuselage.
I got the basic dimensions for mine based on a google search and just copied what somebody else had done, but I don't remember the exact dimensions.
Keep in mind that whatever height you get the spar area, you need to get the tail quite a bit higher for it to set in level flight attitude, so take that into consideration.