"Much laughing and carry on was done when Boeing launched the 747-SP for trans pacific ops. Every one said it would never work long term. I think they got that wrong."
"While in service, the 747SP set several aeronautical performance records, but sales did not meet the expected 200 units, and production ultimately totaled 45 aircraft"
I flew a couple trans-Pacific - SFO - HK IIRC - it was a grim experience even in First TBH (in those days First was roughly equivalent to Enhanced Economy these days...............)
I thnk the main benefit was for SAA who had to fly UK - South Africa round the bulge as they couldn't overfly any African country in those days