Measure CG with main tank empty and hopper tank/UAT filled....gear up vs gear down makes almost no difference on the HotSpot since the main gear retracts toward the middle....the slight change caused by the nose gear coming down is insignificant.....

5 1/4" back from the leading edge, measured at the root contour on the fuselage is a very good starting point........I don't use the leading edge measurements since my 2 methods of setting CG, i.e. suspend the model using a plumb bob, or using a homemade pivot, are most convenient using marks on the fuselage for reference......

About 1/8" or about 3mm up reflex on the elevons also works well at that CG setting....then fine tune after your first trim flights.....

Tom