Hi Aaron,
I have no experience in the building of EQ platfroms. I do have these links you may want to look at.
This is the Stellafane links page.
https://stellafane.org/misc/links.ht...orialPlatforms
Here is a link to a water drip method of tracking (McCreary Fluid Mount), and it is claimed to be very accurate, there is no PE and it is accurate to 1 arcsec drift over 80 minutes.
http://subarcsec.com/index.html
All these platforms track in RA only, so you will need a really good polar alignment to stop DEC from drifting. DEC drifting will determine how long your sub exposures could be.
Cheers
Bill