Mike,
It depends on the type of platform, the centre of gravity of your scope, type of driving method, latitude, the use of the platform (for one particular scope or a range of scopes or cameras).
In short, there would be no definitive plan, you will have to draw up a set for your needs and hope you get it right (that is why these are normally made by tinkerers
as the plans are usually quite fluid). Just use the spreadsheet in the web site I quoted in the article for the actual platform. As for the driving system that is a whole different ballgame and depends on how finely balanced your setup is, the size of the motor used (influences the noise level and how adaptable the system is), standard DC versus stepper motor, tangent drive versus direct drive (my recommendation), how you plan to reset the platform, etc.
PM me if you want to carry this further as I have lots of ideas but that is what they are, just ideas which I am trying at present while my platform is in a million bits.
Cheers