Web Server Connector - old & new

I've got a site setup now that is using the FMU 5 version of WSC on the OLD OS X Server v1.2 ( NOT 10.2 ). And it's setup with Apache and SSL and it's VERY stable. I'm then using Server 5.5 on OS X 10.2 (client) and haev 2 older iMacs connecting to that, one runs OS X 10.2 and FileMaker 6 STD and basically just sends and checks email, and the other iMac runs OS 9 and FMU 5.0

My question is this, if I bought FMU 6 and ran it on an additional OS X box would the old WSC be able to connect to it, and properly load balance with the OS9 mac?

I tried this with Win2k adn FMU 5 and the WSC seemed to hang if one of the machines froze (which of course - in addition to performance - is the whole point of running redundant machines).

Or does anyone know if the NEW (v6) WSC would work on the OLD OS X Server v1.2

(My server is an old B&W 450 G3 and I'm guessing 10.2 would slow it down quite a bit with all the Aqua GUI stuff that I'll never look at anyway. - oh and I tried to use the old WSC with darwin to eliminate the GUI before with no success - but maybe the new WSC would work...)

Anyway the thing is I'd like to have some input before I shell out $$ for another copy of FMU.

My other consideration is migrating the site to MySQL so I could run it all on one box, and keep my SSL - but that could turn out to be more work than I can afford to get into right now.