been in the hobby 10 yrs and this is the first I have ever seen these
What are you, a Newbee?[8D]
Actually, I just heard of them a few weeks ago myself. But that explains alot about the difficulty in removal of engine screws. Personally, I prefer hex heads and have replaced the screws on some engines with them. But you need to be aware of the strange metric sizes, as there are some that have the same pitch but different diameters that can fool you. Of course we also have 5-40's which are very close to the common 4-40 on some engines.