I've never had any problems setting up pull-pull using servo arms on my pattern planes.
As metioned previously, it's all about the geometry, get that set and you're sorted.
Control horn/conection point width must be identical to the servo hole width or visa verse.
Use a screw adjustable horn(s) at the controll surface end and adjust it so its Identical to the servo arm width.
Next check the offset. If the conection hole at the controll surface end isn't directly in line with the hinge line( where it shoud be if you built it in corectly) you'll have to offset the holes on the servo end accordingly. Once everthing matches, it's a done deal.

Regarding straight or crossed cables... it's precisly the same deal crossed or straight.
The only difference is the crossed method allows the cables to exit at a slightly more acute angle that can better suite different aircraft design.
Another point worthy of discussion is the use of the tiller bar. Cables connect from the surface to the tiller arm, then a standard push-pull conection to the servo. This method allows you to get a considerable tension on the cables without over stressing the servo assembly/gears etc. As with any pull-pull the geo' will have to be spot on if you don't want slop.