EZ track oval in an oval question

[dpkopp]

I am running a 18" curve oval inside a 22" oval and connected them with a #6 left crossover. I want to add a #6 right crossover but I am not sure if I need  1/3 or 1/2 sections to widen the 18" oval. I really don't want to buy the wrong track size.

[Joe Satnik]

One 3" straight in the middle of the each 18"R half-circle (end of oval) should do.  (Exact is 3-1/4".)

http://www.bachmanntrains.com/home-usa/board/index.php/topic,11520.0.html

[dpkopp]

I have the 3" straight in place and both the #6 crossovers in place, runs like a champ! Thanks for the help!