I have a '74 std beetle (1200). it is my daily driver. I drive my other cars only on weekends so their batteries remain alive, or once in a couple of months in evenings...
daily clocking is around 40kms and AC is on almost always (even these days). if i'm getting daily groceries (eggs etc) and the family is in the car, i leave it on with AC and have never faced any issues. Since i wanted my beetle to be my daily driver, installing an AC was compulsory. I drive it to work and prefer it over the company provided car.
I've been running this setup for the past 3 yrs, never had any leakage or breakdown and no engine heating issue. The performance drop due to AC load is the same in terms of comparison as in any other car.
I will post detailed pics of the setup after our KHI meetup on 25th as i'd be taking pics of the event that day.
i have the facility to do the complete fitting etc at my workshop if anyone is interested. otherwise, i'll be more than happy to give any advice required.