Alright so I finally purchased a 2nd set of cake pans as it was getting a bit ridiculous baking 1 cake at a time. I do have a few questions....

I exclusively use the WASC recipe, which calls for baking at 325 for 40 mins and it works out perfect everytime.  What I was doing until now is baking an 8" and 6" at the same time but taking the 6" out approx 5 mins prior.  Now I know adding more cakes to bake does SOMETHING to the cooking time just dont know and would rather not mess it up.  My plans is to put my two 8" pans which make 2" high cakes on the bottom rack and two 6" pans to the top rack.  Should I adjust the baking time at all? Basically I've never baked 4 cakes at the same time but once did a tray of cupcakes and an 8" cake and it messed up the cupcake baking time.  I've always had perfect cupcakes at 18 mins but I remember having to keep adding a few mins to it until it was cooked.  

Also wanted to add, I have the convectional oven and looking at the below website I should be baking at 275 for 40 mins compared to the 325 I should be baking in the regular oven option.  I never used the convection option of the oven but looks like it's needed to bake multiple cakes. 

Does it sound about right?

Regular BAKE option in oven:

Bake at 325 for 40 mins

Convection option in oven:

Bake at 275 for 40 mins

http://www.convection-calculator.com/

Baking multiple pans will increase bake time, but not by much. If you become familiar with a recipe and the indicators of a fully-baked product (color, toothpick test, etc) you won't need to rely on time.  

Convection oven temp is usually set 25 degrees lower than conventional baking, but some manufacturers already put the temp differential into their software. The best thing is to read your Use & Care manual.

I never bake one pan at a time. It doesn't feel right.  

I have baked multiple cakes at the same time in a convection oven for years. I just baked at the 325 degrees alternating large and small sizes. For instance, a 10" and a 6" on the top rack and then under the 10" I would place a 6" and under the 6" I would place the 10". Then I would bake two 8" on the bottom. Keep a check on them and remove them when they are done. You might have to rotate the cake pans around clockwise to insure even baking (even though it is convection, this was necessary for my oven). It will take everything longer to cook than it would if it was in there alone. For one, there is more product for the heat to make its way around and two, there is more steam escaping. HTH

Thanks for the advice to go only 25 degrees down unlike the converter calculator. Made a double batch of the WASC and added one 8" and one 6" on the top and alternate on the bottom and baked at 300 degree for 30 mins and it came out perfect.  Saves me 10 mins and I can bake 4 cakes at once..win and win ;)