Guday Mary,
Unfortunately, I don't have an HF trailer frame to measure. The only thing I have is the trailer frame I built to my own specs. If nothing else, the specs may give you an idea that might (?) be helpful to you.
From the top of the axle to underneath the frame is 4.9"
From the top of the axle to the top of the (3" x 2") frame, it is 7.9"
My tires are 25 5/8" in diameter. The top of the tire is 7" above the bottom of the frame (or 4" above the top of the frame). This distance will increase when the TD is finished and fully loaded. Most of this info, if not all of it, may not be of any use to you at all but may give you a comparison to use as helpful data.
The distance from the axle to the frame is also governed by whether you are using "Slip Springs" or springs using shackles. The use of Slip Springs may limit the distance obtained. A Slip Spring often has more "curvature" to try and gain a little more axle/frame clearance.
The really important dimension is specific to your own trailer. This is the distance from the top of the axle to underneath the frame. This distance is greatly influenced by the shape or the curve of your springs. This dimension may not be a standard size among the spring manufactures which is why I am so very limited in being able to help you. I used to work for an internationally known spring manufacturer producing all the drawings of every part that he produced or brought in. All the parts that were brought in from overseas were made to the specs of my drawings and the specs had very tight tolerances and uniform US and Aust. Standards.
The amount of bounce is dependent on the "stiffness" of the spring and the weight of the finished TD. As a general guide, a bounce of 2 1/2" would be the maximum amount on a rough road surface. Any more than 3" and I would consider a review of the springs as this is far too much for a small leaf spring on a trailer.
The Tire cover thingies are called "Fenders" in the US and "Mudguards" in Australia. The clearance from the top of the tire to under the fender must be a little more than the maximum deflection of the axle or the tire will hit and rub on the fender. An inch extra here would be a good start.
Hope this helps you or others reading thru it.
Kody