Everything depends on which block you use since they are all different... but take for example the FRPP Boss block. The cylinder walls allow the piston skirt to extend below them at BDC with a shorter rod. I saw somewhere that the wrist pin is more than halfway below the cylinder wall with some short rod combos. When there is that much piston below, I'd be afraid to spin it high, especially under boost but 7,200 isn't horrible.

Since you won't be spinning over 8 grand, I wouldn't think there would be too much differences between rod lengths. If piston weights are similar, the rotating weight would be higher with a longer rod.. which would lead me to believe you'd have a bigger gain on the torque side. Keep everything as light as possible and the boost would come in quicker, giving the combo a slight horsepower edge.

Just something I'd think of, but I am not an engine builder... and don't want to give the impression I know for fact what I am saying on this. Just thinking out loud.