Are there tugnuts made to fit forward facing horizontal dropouts?
I was able to use a surly tuggnut tensioner with my cross check frame with semi-horizontal, forward facing dropouts.  No slipping after that. The end of the tensioner bolt bolt nested in the opening on the rear of the dropout where the long wheel positioner bolt would be installed.  It would likely work on most bikes with this style of semi-horizontal dropout.

Looks like this:


The newer Surly Hurdy Gurdy chain tensioner is actually designed with the cross check dropout in mind (and should work with most semi horizontal dropouts). It's not going to get in the way of rack and fender mounts like the tuggnut. From surly's site:


  Hurdy Gurdy is another nifty device that keeps a rear wheel from slipping forward in the dropout under pedal load. It’s designed for our Cross-Check’s semi-horizontal front-loading dropouts, and will also work on many other similar dropouts. 


Hurdy gurdy looks like this: