You're going to get immediate responses on these forums "NO!" because the bumpers are too thin, not welded adequate, the torque (bouncing) will rip them off, 4 bicycles is just too heavy, it will reduce your tongue weight, and bunch of other reasons. In all generalities, I have to agree. However, I never listened to anyone, so on all 3 of my trailers I've owned, I used the same one and my bumper never fell off. (Dutchmen Sport, Keystone Springdale, and Keystone Outback).
All I can say is, if you do, do at your risk. Summerland is a Thor Industries trailer, same as my three. I'd probably do it! But you still have to decide for yourself:
My Outback came factory installed with a hitch and it's reinforced with the bumper. So I think my bumper has more strength than my last 2 trailers. We no longer take the bicycle with us (getting too old to deal with it), but I do have a carrier I use. I have not had a problem at all. My bumper is still there.
All I can say is, proceed at your own risk. Check with the manufacturers recommendations.