The varieties of alloys used on welded steel bikes is quite diverse as is the manufacturing techniques. A lot of the "air hardening" ideas spewed about is just marketing spiel; pretty much all steel alloys will air-harden in post-weld cooling. The degree to which this occurs varies based upon the type of torche used and how hot the HAZ was. Personally I've always though the cooling-rate is too quick and would prefer to have the HAZ annealed and spread out afterwards with an oxy-acetylene torche.
This is a common procedure when building roll-cages for race-cars and the debate continues endlessly over DOM (1020) tubing versus 4130 chromoly. In actual practice, 4130 wins on a weight-to-strength basis, but does require annealing the welds afterwards to prevent cracking due to the more concentrated HAZ with the thinner tubing.
I think your procedure is different than what the OP was referring you. Yours provides for significant increases in clearance and requires bending the stays. Given the double crimps already present in your photo, any weakening due to additional bending wouldn't be significant as most of the loss-of-strength has already occured. The OP's dowel procedure leaves the stays intact and just creates a small dent on the inside with a wooden dowel. This is a more common procedure on round chainstays used on MTBs.
Last edited by DannoXYZ; 10-18-09 at 02:09 PM.