Parts for the Taper attachment.and the mounted castingt. They are 2 end pieces made from 1" dia stainless steel I had on hand,  any steel should be adequate.  I made a couple of top nuts, and used a wrench instead of levers to tighten them down.  The cross slide connector and a slide that fits on the .5" dia. drill rod between the end pieces..
The mounted casting and mounting for the connector to the cross slide.  I removed the cross slide screw nut and used the existing holes to attach the connecting rod to the cross slide.  Some day I might try to make a new attachment and cross slide nut that does not require removing one or the other but this works for now. 
The finished assembly.  It took a little while to get the mounting correct for the casting. This adjustment is to make sure the saddle and cross slide work smothly without any binding.  The end pieces are taller than they have to be, but I wanted them to be easily accessed from the front of the machine. 
Using a dti to adjust the taper attachment for turnig a 2mt taper.  With a little work you can adjust for no deflection from one end of the to the other.of the end mill holder I used for a reference .
Here it is in use turnig the taper for what I hope will be a shell end mill holder for my mill.  As most of my tooling is 2-mt the taper adjustment will probably stay set for that.  But since the length of the was made 10" between centers of the end pieces you can use the same formula as with a 10" sine bar to set for desired angle..