There is a new thread on Tventuring to discuss using Harbor Freights Haul-Master #94564 1720 lb. capacity super duty 4’ x 8’ frames as a base for DIY Compact Camping trailers.
From my experience they work well for lightweight DIY camping trailers that will see pavement and occasional well maintained off-pavement towing with little to no modifications. They are also suitable for light-medium duty off-pavement towing with various levels of modification.
From a strength of materials perspective; the frames are fine for lightweight home-built camping trailers. They are engineered for a 1980 lb GVWR (loaded weight). The compact sized DIY trailers most folks are building normally have a loaded weight of 800-1200 lbs, some a little more, some a little less. Also adding a trailer tub or box on the frame adds rigidity and strength. The stresses of off-pavement towing do require making some modifications to maintain appropriate strength.
The majority of DIY Compact Camping Trailers built on HF frames will have a deck footprint smaller than 4’x8’. Generally they are shortened to at least 6’ and in some case also narrowed. Making these modifications to a Harbor Freight frame only requires basic DIY skills.
For additional information review the Tventuring post: “Should I use a Harbor Freight frame for my trailer project?”