blykins,
First you need to know the motion ratio and damper angle.
These give you shaft travel amounts.
The 13.25 dimension is a bit short. but I bet not by as much as you might think.
After all it is on the droop side and you do not see as much travel in droop as you see in bump.
(Note: A bit of a disclaimer, It is very bad to top out dampers from a dynamic standpoint, really strange things happen to the chassis and the driver will not have a clue what is going on. )
Go to
Springrate This will give you your motion ratio so that you can tell damper travel.
If you have any direct questions after you have the data, you are welcome to give me a ring.
But I think it would be best for you to deal with your manufacturer as their engineers will know more than I about your chassis and it's particular needs.