Id like some ideas and opinions on my options for mounting slings to my USC/UMP conversion, right now I would prefer to run a single point but have no means to attach a sling to the rear of the rifle.  I would like to mount forward of the folding stock and have seen the sling attachment screw made by HDPS, but havent heard anything about how well they hold up; Id rather run a QD swivel in the same point.  Any suggestions?

you can QD attache using a UMP stock. I use a single point attached to the sling screw.

Adam has factory HK ambi sling loops for you -
www.hkparts.net/ump.htm