low fuselage trailer ramps

When my Crown trailer ramp is fully lowered my ASW-20 fuselage does not
clear the dolly cradle. Furthermore the scissors jacks require
excessive torque from the fully lowered position. Currently I roll the
main wheel up a small wooden ramp to raise everything a few inches. I'm
interested in other solutions. In particular does anyone have
experience with the screw jack ramp arrangement described on the Cobra
web site? Since a Cobra or Komet ramp won't directly apply to my
trailer I'm considering building my own such ramp. Does anyone have a
source for this type of screw jack in the USA? I have seen similar
jacks used in some older European cars. My web searches on "screw jack"
only return very large capacity equipment.

http://www.cobratrailer.de/english/index.html
The illustration opposite shows different versions of lift ramps for
the fuselage: ...a version with screw jacks, especially useful for
gliders with low fuselage...