I think its a good idea, especially if you add another one crossing it going the other way. Whenever iv seen failed wishbones it has always been at the end of the plate. Must have something to do with the amount of heat the seam weld on both sides does to the steels integrity.
Ive read a while ago, something to do with wishbone tubes should not follow the exact path of any force going though them, cant remember where or what exactly, maybe a real engineer will come along and put me right or wrong.
