Tray Mount Screw thread?

I have searched and Googled to no avail....
The short end to a long, sad story finds me needing to use a non-Ikelite strobe with my
6240.88 housing (for Canon SD 880IS)

Can anyone tell me what the Thread in the housing to mount the tray is?
It is not 1/4-20, that is too big.
It is not 8-32, that is too small.

On another site, someone said "3/16 (10) UNC"

It looks like a 10-24...

Does anyone know for sure? Cuz I'm off to Roatan in 5 days...
Cheers!
M

The mounts on the bottom of the housing are a 12-24 thread.

Regards,
Jean / Ikelite
IKELITE Underwater Systems

Thank you!!!!!

I wanted to mount my strobe tray using knurled head thumb screws. I found that these on Amazon work great, at least on my Ikelite housing for a Canon S95:
Amazon.com: Stainless Steel Panel Screw, Knurled Head, Phillips Drive, #12-24, 9/16" Head Diameter, 1/4" Head Height, 3/4" Length (Pack of 5): Industrial & Scientific