The property I've been renovating has two separate meters. One on the house and one on a detached garage that used to be an automotive shop. I recently upgraded the house to a 200amp service (has exterior disconnect and 4 slots available outside) and I want to disconnect the garage meter and connect it as a subpanel. Solely because the garage electric bill runs more than the house due to the second service cost. The garage panel is properly grounded with rods and I'll be running SER 4 strand cable from the main to the sub. I'll be unbonding the ground and neutral in the garage once it's a subpanel. Adding drip loops and anchors at each connection point. My question is best practice on running the cable. It'll be about an 80-95ft run and underground is not an option without cutting out a lot of concrete. The service line to the garage is overhead with three strands going into the weatherhead (hot, hot, neutral). I'd have to fish a ground in/out to connect to the 4 strand SER coming from the house. The house is rectangle with the panel on the SW corner and the garage located off the NE corner. I.e., the garage is on the opposite side of the main panel of the house.
My question is it's equally easy to run through the attic vs. the exterior/perimeter of the house. In the attic I can save some wire by running the diagonal, house exterior I'd have to follow both sides. If I run through the attic I can either exit through the roof or gable on the side nearest the garage weatherhead. Is there a benefit to either? If I exit the roof, do I need a weatherhead in the sense that I "splice" the cables? Meaning I run the SER in the conduit individually, then I splice from the garage weatherhead to this new weathehead (about 25ft overhead). OR do I keep the SER cable fully intact coming out of the weathehead and then splice at the garage weatherhead? What's the best practice for running about 25ft of SER overhead is basically what I'm asking. Spliced for the gap or unspliced, 2-2-2-4 Aluminum.