Can I bake 2 different sizes of pan in the same time? (ex. 10" with 14")? Normally I bake cake on top in my oven, and never did large cake before, will this bake correctly, or should I bake each pan separately (that would take more than 6 hours). If I can bake together, should I keep switching the pans from top to the middle of the oven?? Thank you.

I do it all the time....since they bake at different times, you have to move them in and out of the oven FAST so you do not loose the heat in the oven. I put the largest toward the back, and fill in with the smaller ones. Just be sure allow for good heat circulation in the oven...no pans touching each other or the sides of the oven. Of course, this will depend on the size of your oven, small wall ovens may not accommodate more than one pan per rack!

I am always afraid to bake different sized cakes together because it seems if I open my oven too soon I always get sinking in the center.

I would love to hear what others do. It would be such a time saver!

I always do that... but not sure if that is the reason why I sometimes get a wet-ish gummy-ish like center.

I would never have gotten thru all the times I have had 2, 5, even 6 wedding cakes for one weekend if I didn't!
Of course. It will effect the amount of time it takes........the more in the oven the longer is the general rule. Sometimes that might be only 2-5 minutes; other times could be as much as 30 minutes extra.
.........afraid to bake different sized cakes together because it seems if I open my oven too soon I always get sinking in the center. .......

You should not open the oven door until you can smell the cake baking. One definitely can tell when they are ready by the smell. It might not be totally ready but you can use that as a good judgment. Hopefully you have a window in the oven door so you can also check things that way. It should not effect baking too much once you can smell the cakes.