SA,
I agree with you in some respects, it does seems a lot of weight for two short bolts and when you consider you have a gearbox to go on there as well plus all the 'grunting' you are going to have to do to get the bits off the ends of the crank.
However that engine has been sitting on the stand for almost 9 years now, I have taken it off about 3-4 time to build other engines with everything attached(gearbox, extractors and radiator) and done a load of grunting, even two people grunting in opposite directions and it hasn't managed to break it.
Unless you are a decent welder, I would get an Adult welder to attach the plate to the pipe, but otherwise just do it.
If you are still a bit nervous I sometimes have the engine crane hooked up and sitting above the stand with a chain attach in the event of something bad happening, but touch wood, Ouch!!, it hasn't.
Terry