Longer is always better.... 12.5" is max for the Savage swingarm...
I have 12.5" Intruder shocks on mine,... better handling and comfort... But not recommended for your weight...
I'm 145lb and ride at full stiffness.  The Intruder shock is very soft...
I still recommend at least 12", but with a stronger spring... Progressive is the high road choice,... adapt shocks off a Sportster for the economy route.... bushings need to be replaced.
More travel definitely makes more comfort and less wheel hop on bad roads....

Taller in rear also shortens front fork rake and adds weight to the front end... both plus's for handling..
You will have slightly less reserve gas in the tank due to attitude change...

ralfyguy wrote on 07/14/10 at 10:47:33:

Right,.. thanks Ralf...

I added a hockey puck to bottom of my kickstand...

I knew that,...   ...

One of my riding buddies here is a big dude like you...  Stock Savage springs are pretty heavy duty...
Intruders are much too soft.
Heavy duty Harley, or firmer Progressives are for you...

My heavy buddy did get extra firm Progressives for his Intruder and found them to be too firm,... so be aware, you can go too far...

I would check into used Harley take-offs,... 11" or 12",... as they will be cheap enough to try, and resellable... $20 to $40... if you hunt around...
Progressive's are a big financial commitment... and you'll take a huge hit on resale... so you need to be pretty confident they'll work for you...

Maybe someone else has more specifics on the right Progressives for you...

But, basically,.. I'm saying that taller shocks are worth the effort, and will make a dramatic difference for you...

did anybody else notice how many times I said "for you"... in that last post?...
How annoying... ...