I think this is one of those cases where it didn't work well for the one(s) that reviewed it, but it may work well for others. I mean one of the main problems that Marty and his partner had with it is that it looked funny to have a dildo coming out above his penis. I think that is sort of the point with this device, so you need to get around how it looks at some point and check it for functionality. The other reviewer said the cock ring was too small, and the way to relieve that problem is get an additional cock ring or rings in a larger size so that it will function well.
CW gave some good advice as well, and I will add that I have no trouble using my inexpensive three-strap harness to hold a dildo above my penis.

Hm, but also a faulty strap... get a basic leather three-strap from a reliable manufacturer, and go for it- any reason you wanted the extra o-ring for the flesh-and-blood penis?

why would a man need this lol