Quote:

... I use the standard shocks and two up I have them as stiff as possible..



I agree.
With all my bikes, whenever I had any front end oscillation (especially two-up) I jacked up the rear shocks a little at a time and it nearly always disappeared.
I have especially noticed it when touring (2-up + baggage) although strangely enough ... never on the Speedy (but that may be because I have the Progressive 440's which I have already jacked up somewhat).

After all, it makes sense that a bikes geometry changes when 2-up (since you have already mentioned that this normally only happens when your GF is on the back) and sometimes just slightly ... is enough.
Try it, it's a quick one ... if it works.

Warning: Do not overdo it because then you will get slightly wobbly handlebars (a mini tank-slapping sort of effect).

Bedouin. Blessed are those eyes that have seen more roads than any man! (Homer).