I think it should be legal, but not in singles unless you want
to see the receiver up near the 7 line. The outside singles serve
that winds up being perfect placement over the cage would piss
off gamblers.
I have no problem with the traditional singles ace serve that
can be returned as a rebote...I've seen Churucca do that many
times against guys like Lecube, often for a rebote carom winner.
There is no chance to return that over the cage outside serve
in singles short of being in the front court when being served
to.
So I'd say the serve should need to hit the green back wall area
(singles only) as opposed to red cushion, so that a rebote return
is possible. I've seen guys backed up to wall receiving and the
server throws in a weak short low serve that hits just past the
4 line and it bounces 3 times by the receiver got anywhere near
it ! Works good against fat backcourtmen.
I think the best singles serve would be one that hugs the sidewall
and bounces so as it hits like 9-10'+ high on the back wall
(very few players could get that) If you come off the wall for
a rebote you'll likely miss entirely or just barely get a weak
return that the server should be able to kill 95% of time. Few
try to rebote a serve, only old pros like a Churucca that can
see it coming... even would only rebote it if was more to the
outside, you can't do much if it is in the corner....jump or climb,
if you are a wall climber sort.
But that over the cage stuff is unfair ! I've never seen it in
singles. Fine in doubles as the frontman had a chance to cut it
off for an easy winner.