If my home office is principal place of business but travel to customer sites can i expense meals, or are there requirements for distance or duration of travel for this?

As long as you are self-employed, you can deduct meals. There is no distance requirement.

For more information, follow this link: 

https://turbotax.intuit.com/tax-tips/small-business-taxes/taking-business-tax-deductions/L5RueYPVS

You may only deduct business meals.  You can't deduct personal meals (like the lunch you eat by yourself).