i have the combo version that has only the 4 ohm speaker output.
i know i can figure out how to put in an 8 ohm output because the red wire is the positive 8 ohm out thats normally just insulated, i could easily just smack that onto a jack, etc.

but how can i get a 16 ohm out when the only thing readily available is the 4 and 8 ohm outs?

'87 Fender Strat
Oscar Schmidt Archtop
Laney LC15R
I was pretty sure that the output transformer has a 16 ohm tap too.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
The only way i have heard to add a 16ohm output to the combo version is to replace the Output transformer.
Heres a nice little doco on modding the VJ, i think the OT replacement part starts on page 11 or 12

Also sewatt.com is a pretty good resource