I use as much domestically sourced material and tubing for my frames as possible. In general, that means I use a lot of tubes from True Temper sports, primarily their OX Platinum and Verus HT lines. I also use plenty of 4130 cromoly for smaller bits, and bottom bracket shells and dropouts from Paragon machine works.
This does not mean that I will not use other tubes and dropouts if appropriate - I start from scratch with every design and use the tubes and parts that I feel will work best for each rider.
Got a question about tubes or frame parts? Drop me a line, I'll be happy to chat with you about it.