I'm with Rogue, I've got the Kaymar and haven't had any issues yet. It doesn't seem to be as strong as Slee's where the bumper returns to the wheels but gets the job done for quite a bit less money. I got the double pin delux bumper with one tire carrier for 300.00 less than Slee's. The bumper bolts flush to the rear crossmember so unless that is cut off before installing Slee's I'm not sure how the departure angle is improved.
OK, we sell all three bumpers, Kaymar, TJM and ours. So I think I can be impartial
Kaymar is a great bumper for towing & expedition wheeling, but it does hang lower down below the cross member, although it does wrap the rear of the crossmember the same as all the others. It is mostly the receiver that hangs down. Also, it does have two pivots which allows you to take the whole house with you on said expeditions. The wing supports are not great, and the corners are big, boxy and low. The tire carrier is not bad and will accomodate a 315 tire.
The TJM is a lower cost option, can be had with two carriers. Also, the hub is built into the bumper, so when you have no carriers, there is no spindles sticking up. It does have nice rubber caps on the ends and the corners are pretty small and tucked up. The wings are not very strong and the supports are also not that strong. The bumper wraps the crossmember, but the bottom is not turned in again. That leaves a lip that can catch and bend when you drag it over rocks. The tire carrier sits fairley low on the bumper and you can not run a true 35" tire on it without modifying the mounting piece. No receiver but the holes are left open on the back of the crossmember.
Slee bumper, it only comes with a single carrier, but it is high mount and takes a 37" tire. The wings are strong and well supported. No receiver, so if you tow 6k lbs all day, it is not for you. The corners are tucked up high and have about 3" more clearance than the Kaymar. The bottom lips are all turned in, and you don't hook it when you drag it off rocks.
Custom, well that is always the best since you can get exactly what you want, except in most cases, the cost would be a problem, unless you have a buddy that will make it for money. Or you have all the tools & stuff and want a fun project.
Simmons, I recall seeing a rear spare tire mount in the SOR catalog for a single gerry can. I'd be willing to bet that your Slee carrier could handle the additional weight. You might want to check that out. I've seen similar items on Jeep websites, too.