As you say, almost all of the early 650's suffer from twisted center stands, but the problem lies not in the stands but in the stops. The OIF bikes incorporate the stand stops into the mounting ears, which are welded to the cross tube. The cross is very thin and was not gusseted to the down tubes on the early 650's . Starting the bike on the stand, heaving the bike onto the stand or sitting on the bike while eating pie can all cause the cross tube to twist until the stand legs face forward at an extreme angle and the bike leans to one side or another. A quick search of the internet found this photo:
Notice that both wheels are resting on the ground and the only thing stopping the stand/mounts from twisting further is the foot peg of the stand contacting the ground. Eventually the primary side mounting leg and ear will stop bending while the timing side continue to do so, then the bike will begin to lean to the right. Also,notice that the bike will need to be lifted quite a bit in order to get off the stand, instead of just pushed forward like most Triumphs. Here's a photo of a bike with straightened and braced stand ears and cross tube:
One wheel or the other (depending on the fuel load) is about 2 inches off the ground and I can roll the bike both on and off the stand while straddling it. The solution to your problem lies in straightening both the stand and the cross tube, then bracing the cross tube to prevent twisting. I have both a poorly braced 650 frame and a factory braced 750 frame I'll post pictures of in the next few days, if anyone is interested.