I agree with 'Six', the 'trail' (placing axle behind the centerline of the strut itself) is the same as caster and the wheels won't come off of the ground with this set up (like seen on full size F-4 nose)

To be more clear on what I stated - your retract (where the steering pivot passes through) has to be 90 to the surface. The strut doesn't matter above or below the oleo section, if it (the retract) is angled to give caster, the wheels will lift.

Dennis