That is excellent information, explained very well. Thank you. I'm somewhat challenged looking up information in both the forum and the WIKI because of very slow internet speeds. You answered several issues I've been wondering about. I have not worked with bevel angles much below 25 degrees and am concerned about the potential for creating thin cross sections. The four to one guideline is a gem. The razor I will be working on is 5/8ths wide and the spine is 3/16ths thick. Applying your formula results in 3.3, so it seems like I should be fine using the spine as an angle guide.
If the spine had been worn down to 1/8th thick that would result in a 5, and potentially too thin cross sections, correct? Do you guys have a chart that converts these ratios to bevel angles? That would be pretty interesting.

Regards,
Bruce