Obviously there will be some issues based on size and I suspect it would be impossible to replicate your Dojo Cho's actions if he is 6'4" and you are 4'4" and you will have to make adjustments. In those cases, explain to your class how you are deviating and why; showing both your Dojo Cho's technique and the one you have adjusted to. Just make it clear which way is the "expected" way and which is a variation you've had to adopt.
In any event, I think you are obligated to teach the Dojo Cho's technique regardless of what rank you are while you are a member of his dojo.
Ultimately, I think this is a question for your Dojo Cho. It is likely that there are some aspects of technique that he considers non-negotiable, and some that are body type and/or personal preference and/or uke-dependent. The only way to find out which is which is to ask.
As a student, one of the advantages of training at a dojo with instructors from different backgrounds is that you *will* see different variations. Depending on how it's handled, this can be either very confusing or very helpful.
In my own classes, I will often say, "Sensei will yell at you if you do it *this* way, and here's why" or "X, Y, and Z all work, I don't care which you do, as long as you incorporate *this* particular body movement that I'm focusing on."