I would like to reduce the horn lenght of a JBL 2397 wood horn. The amount removed would be about 7" making the width equal to the cabinet width (Leaving the curved profile).
If you don't like your 2397 horns I would sell them on ebay, or hold onto them, as the old JBL stuff only seems to increase in value. They regularly sell for $500 a pair on ebay. Then you could buy yourself some horns more suitable for your cabinets or build yourself a pair of the correct size out of plywood. Once you modify the 2397 horns they will have no resale value, and if they dont work out you will be out a set of horns and $500.