Help with tubing on Ti frame

[torreyho]

I was hoping for some help with Ti tubing sizes. I have placed a deposit with Waltly and am in the process of getting a hardtail MTB designed. But I am having some trouble figuring out what kind of tubing sizes I should use. I'm not sure what size is on most bikes these days and don't want to go too large nor too small. Anyone have experience with tubing diameters?

[Tijoe]

I would approach it from a different direction.  Give Waltly the frame geometry you want for the frame.  They will design the frame based on their best known practices.
They will send you drawings of the frame.   Review the frame drawings.  If you decide you want larger or smaller tube sizes discuss your proposed changes. 

When I had my custom frame designed, I discovered that about 80% of my frame consisted of standardized tubes and parts.