I never quite liked that, since it could lead to starting stats higher than 18, and I abhor anything that could possibly lend itself to min-maxing.
Elf: +Dexterity, -Constitution
And then you just roll stats as normal, except that if the elf's constitution is higher than the elf's dexterity, you switch the two stats? It still lends itself to fictional consistency (elves are nimble but not very sturdy) while keeping elf stats in the same bounded range as the other races/classes/race-classes. And you still have the opportunity to have an elf character who has constitution as high as the human--it's just exceedingly rare.