What might be the best way to see if its actully pulling timing before you spray.?? What has everyone else done?

I was thinking of hooking it all up, setting it for retarding at 6*. Get it on the dyno with it off, then with it on. I am sure you will see ~30hp drop on the dyno with that much pulled, right?

But, I was thinking about setting the window switch on a 1st gear lock out. The car will never shift on a dyno so the tuner will be pulling timing as it will be activated, but the WS is keeping the spray off as its waiting for a 2nd set of RPM's but will never see.. Does this make since? I just want a double check to make sure the timing is being pulled.

So, whats the best way? Thanks.