Can't comment on the 8'er but.....
I used to ride around a 6'4" for years in the 80's and 90's, then pretty much stopped surfing for around 10 years (mortgage, kids, ross river virus, dud shoulder, moved back to Perth etc), but still played around a bit on a beat up old 9'1" longboard that I 'acquired'. It was a typical low volume Bruce Montgomery design with a fair bit of rocker, so not that flash for paddling in for a board that length.
I was heading to a wave location up the coast last year on a kiting trip so decided to get a new surfboard for when the wind wasn't up and get back into it, went for a 6'8" fairly standard shape with a fair bit of volume, had fun but still struggled from lack of paddling fitness and a few extra kg's.
I just recently purchased a 7'3" 7S and have had two sessions on it so far, only in small mushy stuff but was super impressed mainly at how easy it is to catch waves on, it is actually easier than the 9'1" BM and rides waaaay better.

My plan was to just get out a lot more and get some paddle fitness back then drop back to a smaller board but I think I might get used to this, hanging to try it in some half decent size waves.