I changed the screws on the drivers at the same time as the peg screws as noted in my earlier post. You may notice that the new screws on the drivers are less noticeable than the stock screws. I think the new ones are meant for electrical outlet covers. I thought that the sound improved as far as better detail and more distinct imaging. This was also noted by a friend of mine who remarked, without being prompted by me, that it sounded more "solid". This could also just be a product of the speakers breaking in, but the change did come right after putting in the new screws, which are tighter than the stock ones were. I'm no scientist, but my personal opinion is that the dfference is mostly due to the new screws on the drivers, and I doubt if the different screws in the peg holes made much of an audible difference. If you are worried about resonances, I would think that the pegs, with their greater unsupported surface area, would be more prone to resonances, as well as sonic reflections. But like I said, I personally doubt that it makes much difference, just my unfounded opinion.
In any event, you can easily go back to the pegs if you think the replacement screws don't sound right. And the cost of the screws is so low that it's not a financial issue to experiment.