Having adjusted both an L and an R, I would have to say the "confines" are much tighter on the R. I bend a few fins on the radiator every time I do it.
I trim a piece of cardboard and put it in front of the radiator to protect the fins.
I don't pay much attention to the "T" mark. I pull the spark plug, roll the engine, make sure it doesn't roll backwards, watch the rockers and when I hit the flat spot on the cam, I check the clearance. I also watch the piston come up to TDC by watching a dowel rod move up thru the spark plug hole.
I do use Motion Pro feelers.