Hey Stephen, great post to put up in case anyone has a similar question
The main factor at play here is actually the change we made to the router mount of the LongMill MK1 in early 2021. That mount is the same one we now use with the MK2 and the 2 main changes were:
make the mount thicker to transfer more rigidity from the z-axis to the router body
modify the mount design to accommodate longer bolts
The reason for the second change was that the mount was using M5-12mm bolts and that size hardware wasn’t being used anywhere else on the machine. With the revised mount accepting M5-25mm bolts we didn’t need to worry about the shorter bolts adding to assembly complexity and made the machine just that much simpler to BOM and order on our end.
What I’d recommend is that for anyone using the old mount - you should also be able to reuse the old bolts that it came with. In your case though you’ve wound up in a special place where you had an old one on hand but without the bolts. For our thicker 80mm mounts shipped with MK1s and MK2s though the 25mm bolts should work as outlined in the manual
As far as specifying size, that’s a factor of us doing some ongoing construction to our inventory management system. We still do have the different mount sizes available so if anyone is looking to get one they can confirm with us via our contact page until we get it working with the shop again
Is that for the reason that you’d like to save a bit of money, or just that you don’t find the extension cable useful? I suppose in your case since you’re using the spindle the extension won’t be needed