That sounds about right 10 Minutes to get right at 600. The times I cooked on it I used the pci grates. I did find some cast iron grates before I gave away, and I gave him both sets of grates. But I don't know if I cooked on it using the cast iron grates.
But, I remember thinking the distance from the burners to the grate was more than I thought it should of been. But I do remember it cooked chicken and burgers very well with no flare up's.
I know if. Took out both grates and turned one sideways and set it on top of the bars I'd give u a killer sear.
I like how u did the polyurethane, I just rubbed the wood on mine with linseed oil. Yours looks much better.
I only had to get flavorizer bars and went with the 20ga SS from Rivers Edge on amazon. (cheapest I could find in SS)