The discussion on these forums is both a) to further peoples knowledge, and to make sure problems don't occur. Granted we've had our share of mental masturbation type posts here in our 5 years, but I think even those that aren't directly discussing a problem that has occured, do have value all the same. I like to think that our little community here is well educated, and will always take in more information than is needed to make a decision just to be sure that they are well informed about the topic at hand.
"I know of no failures in the 8 years we've been making them" is fine and grand, and I'm happy you haven't had to deal with any issues evolving from those failures. I don't doubt that the thickness you've copied from HKS/etc. all has been very well researched and documented by them before they made it, and using that R&D to your advantage by copying what they made is intelligent.
However, I can see in the picture that Clifton has posted that the Greddy/Trust unit has a radius in the place in question. Your thickness might be identical, but there is more to the equation than thickness.
I'm not suggesting that it's going to fail. I'm simply suggesting that in engineering terms, any chance you have to eliminate a stress riser, you take. Especially when it is so simple in this case to do so.