Is there an ideal position of the rear axle in the dropouts? Is center best? Is it a personal thing based on wheelbase preference? Is there a dangerous location - say at the very rear of the dropouts? Curious as to know if I should be adjusting my chain length when adjusting a tooth +- here and there for gearing. Thanks.

As long as your bolts are completely in contact with metal (i.e. half of the bolts are hanging off the rear of the dropout), and your tire isn't rubbing your seat tube, the track ends are there to be used.

Thanks, Nagrom - are you referring to the axle nuts (full contact of the nut, nothing hanging off the back)?

Pretty sure he meant "half of the bolts aren't hanging off the rear.