Units system nuissance

It seems that all of the various systems of units Mathcad offers, they are all "absolute," i.e., mass is a primary unit and force units are derived from it. Nearly all of my work uses a "gravitational" system in which force is a primary unit and mass is derived from that. Most commonly I use lbf (although I would prefer to label it "lb" as the force unit and slugs or lb-mass (which I would prefer to label "lbm" as a derived mass unit.

The nuisance arises because, in any calculated result including the unit of force, Mathcad insists of displaying it in units of mass. For example, if I define F1 := 10*lbf and then ask Mathcad to display 2*F1 = ? it will give me the answer 2*F1 = 20 slug-ft/s^2. I have to convert this to display 2*F1 = 20 lbf. I have to do this all the time and I get tired of it.

Is there some way to change this behavior? I'd like to define a custom units system, but apparently I am limited to using mass as a primary unit and I want to use force.