The differences between the model 2 and the 5 as for construction of spars, the 2 has extruded i beam thru center of spar,all the way thru, the 5 has a builder inserted i beam at the strut mount , and i believe the diameters of the spars is different, the 2 is a little smaller? Not positive on that.
I do know as i said previously i have done mild aerobatics in my model 2, no passengers, the most "G" load positive i put on it was at the bottom of a loop, with out a G meter on board, keep in mind my speed was held below 75 mph , and i'd be willing to say i reached 2.+ G but not exceeding 3G, calm air always for aerobatic anything in the 2, as for thermals and G loads, the wings design reserves any rock hard thermal bumps in the sky, you get lift and allot of it to the point you will see flex in the wing outward of strut mount location, at worst 1" deflection , which isnt allot considering the distance from the wing tip back to the strut, and with proper washout the load is distributed evenly between fore and aft spars,

What's your plan that your concerned with the "G" loads?
If you would like to see an example of how much these type spars can flex under a load, there are 2 photo's in my profile photo album of a round spar load test, the spars in photo are smaller the kitfox spars