Kegging small batches (3.5 gallons in Corny Kegs)

I just brewed my first all grain batch, but due to the constraints on the size of my kettle (only 5 gallon), I can only make 3.5 gallon batches with the help of FermCapS. I also just put in my order from kegconnection.com for 2 corny kegs and lines.

So being a kegging newb, what issues should I be concerned about kegging small batches?

I'm thinking to purge all the air out of the keg prior to racking. That way no air should be in there at all. And/or purging after racking. Any advice is appreciated.

I don't see any problems with kegging smaller batches. After the beer is in the keg, fill with CO2, purge the air by opening the release valve for a few seconds, and then turn on the CO2 again.

How bout if I don't plan on force carbing the beer and use priming sugar? (This is just a what if in case I ever want to go that route)

use beersmith to tell you how much priming sugar to use

or mr tastys calculator

add your priming sugar, and just make sure you purge the keg first

The extra head space will throw off your priming calculations for natural carbing.

Scimmia, any way to compensate for that?

I'm sure there's a formula somewhere that takes more head space into account, but I have no idea where it is.