It seems to me that there is a big difference between 8-ball and 9-ball when it comes to these higher handicap vs lower handicap matches. On paper, it doesn't seem significantly different, but the way the games play out, wow...
Let's use the OP as an example. SL5 vs SL2. In 8-ball, that's a 5-2 race in games won. Not easy, since an errant 8-ball early could tip the scales, but the SL5 can usually control the cue ball well enough that if/when he misses, the SL2 isn't likely to run out and win the game.
Contrast that with his example of a 9-ball race, 38 points to 19 points. Every ball counts now (and the 9 counts 2!), not just who gets the 8 in first. The SL5 has to be very, very careful not to leave an open table, because even though the SL2 might not be able to run them all (though in the LO's case he did!) he can make enough of them to add up, quickly!
I play as an SL5 in 8-ball, and an SL4 in 9-ball. I really enjoy "playing up" in 9-ball, moreso than in 8-ball. (It's always fun to play better players, but sometimes I'm talking about the team as a whole and what we need to do to win.)
My best friend is an SL7 in 8-ball (doesn't play 9-ball currently, so we "assigned" him a skill level of 7 for the sake of it) and when it's just us at the pool room practicing we play races. Even though my friend isn't a big fan of 9-ball in general (the slop/luck factor turns him off, and yes, we play call pocket for our 8-ball games in practice) I think he is really enjoying the challenge of having to work hard to beat me in our 9-ball races. And he doesn't do it every time, we split even the other night, 2 wins apiece. He wins our 8-ball races by a bigger margin, and more of those races.
Seems to me that it works, reasonably well. (I know, except for the sandbaggers, balh, blah, blah.)