Yes, I have split my trips a few times. Portland first then Negril and vice versa. I tend to like negril at the end because I usually fly in and out of Mobay.

I have used a private driver and have rented through Island and drove myself.

When driving myself I usually spend the first night in Mobay and start the next morning to Portland.

I have not taken the Knutsford so don't have personal knowledge.

The drive is long but the road is good and there are a few good places to stop a long the way.

For Private transfers I have used and trust Warren & Kemar McKenzie - brothers from Portland
Warren 876-883-9081 wgam84@yahoo.com
Kemar 876-891-6171 dainianm@gmail.com