PD
I can understand your concern and would support your claiming through VA (or the Canadian equivalent) if there were evidence of harm from what your father did for his country. I am aware of no evidence in favour of your claim but I am an enthusiast in the subject (as a doctor more than a pilot) and so my opinion is far from definitive.
There have been many aircrew doing considerable amounts of aerobatic flying for quite a while now. The community is quite close and haemorrhagic strokes (bleeds as opposed the embolic (clot) strokes) are less common. I would expect that if there were a higher than expected number of haemorrhagic strokes in this population, someone would have noticed and published it.
That said, no evidence does not mean there is no link!
I hope you find out what you want from a definitive source. I have a contact at the RAF CAM (and I am sure he is on PPRUNE but I don't know his screen name) that I could ask if you like
Bob