@Tom Spyrou: The "Tiny Tapeout" runs like a processor in debug mode, every project driven through a scan-chain-like loader. So there are no specific timing constraints on anything, and I think the best way to deal with the timing is just to design it so that regardless of whether or not you know what's in any of the macros, the timing is correct by design---if there are any violations, you just slow the clock down until there aren't any. The timing within the scan chain itself should be properly analyzed and handled by OpenROAD.