wholeman:He has two No. 6 turnouts made by Bachmann. What is the radius curve needed that comes off the frog so he can complete this siding.
I presume what is desired is that the turnout comes off the main and a reverse curve is needed so the two tracks become parallel. The radius really has nothing to do with it.
A #6 turnout has a departure angle of about 10 degrees. So one needs a piece of track that turns 10 degrees. Looking through the Bachmann catalog. In HO scale. Theoretically a 1/3 section of 18" radius should do the trick (Bachmann Product Code 44530).
A 1/2 section 22" radius is 1.25 degrees to much but could probably forced (depending on how long the siding is going to be).
Ideally think the pre-built crossover might be the best bet for nice parallel tracks.