Where should the putter shaft be on a face on putter and long putter?

I am building a long putter and would like to be able to use it as a standard long putter and a face on putter. Can I use a putter with the shaft in the center of the club head as a standard long putter without running into any problems? Can I use a putter with the shaft on the heal as a face on putter without running into any problems? I saw this site www.thewayputters.com and being able to do something like this would be ideal any idea how the lock the shaft into the different locations? Thanks for any advice.