Hi Rom, if you feel a bit overwhelmed about building the English fork mount for that size OTA and you decide to look for a commercial solution.
Then have a look at the Mesu 300 Mount, it is designed for 50cm apertures weighing over 100Kg, fitted with Renishaw encoders it will give you goto and tracking accuracy of 0.02 arcsec.
Pictured below is the Mesu 300 sitting next to the Mesu 200.
http://www.mesu-optics.nl/mesu300_en.html
Cheers
Bill