There is absolutely no issue with letting the right seat do the checks while the left seat taxis - As long as there is one set of eyes watching the taxi. I've been doing this for a while now out of HKG and the last thing you want is to delay your position in line while you have a load of heavies ahead and behind you. My first hours in the airplane (stateside) I insisted on holding at the end and doing the runup then (nothing wrong with that either).