W&B for Arrow

Hi!

Anyone got a default WB graph for an 180 hp Arrow?
I am entering info into a computer programme, and can't seem to get it
right....

The ones I have tell me that I can't fly with myself and my wife in the
front, and my son (age 12) in the back with full fuel.

Can this be right?
I did a calculation manually a while back, and it seamed ok, and been flying
like this a while, so I'm thinking I have some messed up numbers.
Or is the 180 hp Arrow simply impossible to load?

To adults in front and full fuel is not possible either according to my
programme.....

Any ideas?

Frode