Good thread. I may also want to do the IMAC thing. It's very popular in my area.

For me, the reason a light plane is better is that it's just simply slower. More time to do a maneuver, more time between maneuvers to get back on line, more time to do good landings, and more time to compensate for wind. Remember, wind blows on heavy model just like a small model. The only advantage to a heavy model is when the wind abruptly changes (gusts) and the greater mass accelerates less. F=ma

I have slope soared gliders with 10 oz/sqft in 20 mph winds. Its not a big problem (except your upwind ground speed in very slow).

When I had my beloved CG Ultimate, it had very light wing loading, a big wide fuselage, and handled wind just fine.

Bottom line for me is the more time I have to fly the sequence, the better I'll fly it.