[syslinux] chain loading Syslinux 3.86 from 6.04

[Max]

Hello,
   I was wondering if someone might give me a hand.  I have a multiboot
drive I maintain and I am trying to add the ESXi installer to it.
   It seems well documented that VMWare uses their own mboot.c32 file which
is built from not the same code in SYSLINUX mboot.c32 3.86 . I'm using the
Syslinux 6.04 from the Ubuntu repositories.   I have compiled Syslinux 3.86
.  I thought I could try to load the older version of syslinux by
chainloading it.

This is what I have in the config:
COM32 chain.c32
APPEND FILE=/ESXi/syslinux

syslinux is the compiled 3.86 binary.

I get :
"WARN: The sector won't be mmapped, as it would conflict with the boot file.
Booting...."
It just hangs there.

I am doing this in good old BIOS mode.

Can you guys shed any light on the error and give me some indication of
what documentation to read next?

Is this even possible?

Thanks,
    Max