I figured that I would relate my recent trailer experience for others to learn from. I started when I got a new truck with an incredilbly small box, too small for bikes. Then came the nice canopy and so a dirt-bike trailer was required. I am low on driveway space so need a small low trailer that could park under my boat trailer. I started with a common 5x8 flat deck available at Walmart, "Versasport" brand made by snowbear, 1600lbs rated GVW. Probably 90% of the small trailers in my town are Snowbear. I was originally going to build one but it is far easier to start with one. It was easy to get 4 full size bike to fit, 2 on the ouside frame rails. However, first easy 30 mile trip and the trailer started to bend laterally at the outside rails. Turns out this trailer is braced poorly and not up the task. I ended up having to weld a twin front member and number of supports underneath. Then I discovered that the tongue was not centered so it took some sledge hammer work and a bunch of welding and extra supports to make it right. After helping someone on the side of the highway replacing his bearings I figured I better check mine. One had NO grease and the other was 50/50 grease and water. Cheap offshore bearings inside but I just repacked those. Then the tail lights started working intermittently - cheap design so need to replace those. By this time I had only 50 miles on the trailer. Yikes!
In the end, the trailer actually works very well now. Recently pulled it on a 2000km trip (inluding 300km of rough gravel) with no issues (bending). I just hadn't planned on all the additional work. I now wish I would have taken the time to build my own. I guess the moral of all this is that for any members considering using this style of trailer for more than 2 bikes should expect a bunch of extra work. Hope this helps someone. Cam.