It is possible to adjust the front end of the cable from the back. Loosen off the cable end locknut on the front. Make sure the cable end locknut on the back is tight. Pop the cable end off the ball at the back and rotate it to adjust. Be very careful not to wind the threaded bit of the cable right out of the cable end at the front, although if you do it is possible to reattach it without taking everything apart (Yep, I did it!) One thing to keep in mind is that the cable travel is limited internally to about 1" travel, so you don't have a lot to play with.
After getting everything back together yesterday I went for a really nice test drive along the river. All forward gearsworked great but reverse was hard to engage with grinding.
I figured that one turn of adjustment would sort it out as it was very close. Today, anticipating a quick half hour fix I had at it and ended up trying every possible combination of adjustments. That's when I found out about the internal travel limit and also when I found out that my gearlever assembly is knackered. The combination of wear in the nylon bushing that converts the vertical movement of the cross gear assembly to back and forth movement for the cable, and wear in the shift lever bushing where it sleeves over the cross gear rod causes the counterweight to foul on the cables. There really is very little clearance under there so the accumulation of small amounts of wear creates a problem. To top it off the excess play also meant the gearlever fouled on my nice new MK II gearlever surround
The net result is I'll be driving the old rattletrap TR until I come up with enough cash for a slickshift. (Which should solve the problem he says optimistically)
Cheers,
Rich