22.5 degrees seems like a lot of down angle, you can find your original down angle by removing the tire. The square axle shaft where it comes through the arm and is welded was originally positioned so two of the points where parallel to the frame <>
- Remove the tire so you can see the arm and where it attaches to the axle.
- Then use a jack or pry bar to position the arm so the corners of the axle shaft are aligned in the original position like so <>
- You can now see or use a protractor to measure the down angle the arm the tire mounts on originally had.
You probably won't have to actually measure down angle because it is most likely one of the standard ones (0, 10, 22.5, 45) so they are visually pretty different, with 0 being arm parallel with trailer frame and 45 being half way to straight down. Anything different than stock start angle will change the height of the trailer. More so if the shop welds a riser to deal with the next issue, the brackets.
Standard torsion axle the bracket that welds to the trailer is off set so it provides a longer weld toward the tire spindle, same direction the arm is pointed. That is where the load is focused at the tire. On a scamp however the axle is welded in right where the frame drops for the main floor. It is tucked into the corner formed by the frame going up for the rear dinette. No room for the axle mounting bracket to extend toward the front.
That means an exact measurement of the bracket and it's position OR welding a riser onto the frame to make the raised part of the frame level with the main floor so the long side of the bracket can point forward. Using a riser will place the axle a few inches lower so even original down angle axle will raise the trailer about as much as the dinette floor is above the main floor. Starts to make that step into the trailer require an actual step.
What the trailer guys that replaced mine did is figured out the original spindle height from the original down angle and ordered axle with down angle and low profile bracket to reproduce that original spindle location. This provided "stock" ride height for trailer. Helped that they drive down to an axle factory in Indiana about once a week and could talk directly with them to go over a shop sketch of the axle they wanted.
These guys are third generation working in family trailer fabrication business and they did not want anything to do with converting my trailer to a trailing arm axle. Despite the extra hassle of ordering the custom axle they preferred that to trying to re-engineer a trailing arm.
First picture in this Dexter literature you can clearly see the "diamond" running parallel and the bracket is longest in the direction of the spindle. Which is backwards of a scamp leading arm bracket. Turn that standard axle around and the standard bracket won't fit in original location.
I would get the standard 5 bolt pattern not the 4 bolt. Brake hubs for 4 bolt are harder to find as parts and more expensive. The hubs were $50 each and only Dexter had them in stock. If you stay with 4 bolt might want to consider picking up a spare 4 bolt hub with bearing in it because not likely to find it in stock on the road. Mount it directly to the spare or stash it in the camper. I wish now I had done 5 bolt instead of the original 4 bolt. I went 4 bolt to avoid buying new rims but spent almost as much extra on the brake hubs.
To use 5 bolt rims and mount a spare tire on the back you would need to modify your spare tire bracket to line up with the 5 bolt pattern. The two existing spare mounting bolts don't line up with the holes on a 5 bolt rim.
This is a pretty easy. Essentially just a channel with bolts in new location that line up with 2 of the 5 bolt holes on the rim, and 2 holes in the bracket that line up with the existing bolts on the trailer. An adapter if you will. Maybe a bar or channel running down to the bumper to form a "T" with the bracket adapter, gain some support from the bumper for the spare tire.
If I had figured out the spare tire mount before I ordered the axle I would have definitely gone with 5 bolt hubs. Between new rims and not knowing how I would mount the spare I went 4 bolt, regret it now (but not all that much).