Neat !

How did you velify the 5V tolerance on the 3.3V chips ? Checking for excess current on the IO pins ?

Yes, extensively measured with a scope. Most boards anyway fail to drive proper 5V on their DRAM address lines for long.
Also cross checked to the fact that Compaq and others like Memory Masters are also using a bunch of these chips on 5V modules. https://www.ebay.com/itm/124443425899

So far I've used the A1 board with my 486 Gemlight board for almost 6 months (next week December 12).

If you want to be extra safe you can always stick to just using the 5V chips. I had considered making a level shifted buffered module, but the required shifters increase complexity and cost unreasonably.
maybe in future when I decide to make a parity module.

Ok, good ~

I have one suggestion regarding the SIPP holes, they should be moved higher up. I had them at pretty much same height on 4MB SIMMs I made and I had a report of the holes aligning with contacts of the socket on one mobo, making the sticks not work until holes were filled with solder.

I like the logo *notbiasedatall* 🤣

Ah, thanks for that suggestion. I had some concerns about the hole height as well.
Might just adjust that later when I got time.