If you just need a small amount more bottom runby, Take the safety channels (normally 5" or 6") and replace them with two 4" channels sandwiching the stile gussets between them. four of the 4" will be stronger than two of the 5" or 6" channels. Gains 1" to 2" of runby at the bottom. It however will cost you some of the top runby. Works where the Jack head wasn't put in at the right height.