A little heads up regarding plate glass for flattening components. I was loaned a piece of thick plate glass big enough to take a twin crankcase half. Check the glass in several directions with a good straight edge first. (I didn't.) It was not quite flat!
Because the casting is so large you end up with a dip or a high point in the middle depending on which way up you have the piece of glass. If it is too bad you will struggle to get a good joint when you put the halves together. The cases on my "B" cases are so thick and stiff the through bolts struggle to close any gap. I have had a leak that has annoyed me all last year so it is coming to bits any day now for a rebore and I will look to see then if I can find a good jointing compound to seal the gap. I dont want to remove any more material from the crankcase joint faces if I can help it as the end float on the crank assemble will be too small.
What fun we have working with old bits.
I checked it against two cast iron parallel straight edges only to find that the glass is almost straighter than my two parallels. Put the two parallels together and can see daylight in between. I can now use them for door stops or yard art.