A few things to look at:
1) Distance between bearing surfaces on the fixed channel. Does not look like much in that photo - maybe 4 inches ?
2) How rigidly the rods are mounted to the moving front plate. I see some bosses cast into the front plate, and longer engagement is better, but strangely, the rods look to be recessed from the front.
3) Rod diameter - 1" would be very good. 3/4" would be just OK.