@User: I have not given a lot of thought to which pads might be swapped out. I would want to know exactly what you are going to replace them with. I don't expect it to be a problem, especially if only a few projects do that. There is an assumption that anything outside the user area is "untouchable" and may be swapped out for an equivalent layout. But if there are a few user projects that modify the padframe, I should be able to deal with it. One thing, though, is that you cannot remove solder bumps. You can use the space in the middle for an inductor.

@Tim Edwards Thanks. I'm also trying to understand the reason for the restrictions on what we tape out - From your response, clearly the chips are going to be used for something other than just giving them to us, otherwise you would not care what we put as long as it is useful to the community, not illegal, and doesn't break the fab or ruin the whole wafer. I can see that anything that causes you to have to do manual verification per design is going to be unattractive. I can also see that if you want to change the design of stuff outside the user area so close to tape out that we don't have time to re-apply our modifications to it, then you would have to do that work, again undesirable. In the worst case I could wash off the polyimide with nasty solvents (NMP) and wire-bond to metal in the user area, but that makes it unfeasible to share many sample chips with others in the community, which would be sad.

@Chris Jones: The whole thing has to be pretty well streamlined or else it won't happen at all. There are only a handful of people here preparing the PDK, designing a chip, building the website infrastructure for submissions, all of which is being done from ground up. I would prefer to lift as many restrictions as I can, but not for this tapeout.

@Tim Edwards Fair enough. Thank you for all of the work you are putting into it. It gives us a great opportunity.