Insert beam with default start and end extension.

[trevorL3DU3]

I'd like to create a brace family that I can insert with no further modifications required.  To do this I wanted to pick the 2 insert points as the hole locations.  I've got the Z justification work as the origin, this works well.  What I can't find any information on is having the default "Start Extension" and "End Extension" set as something other than zero.  I really want it to be "25":

Can anyone explain how I can do this?

Thanks.

[semi]

The reason you can't do this is purely because beams get joined to the walls or columns you're modelling it onto.

If only Autodesk would listen to us and make us choose to place beams with an allowed join or a disallowed join before modelling the beam this topic wouldn't be an issue.