Thanks and that's a +1future_canadian said:Your reference letters should be accurate and reflect what you really do. However if you can emphasize your 2172 duties while remaining accurate, I'd do that, as 2172 has space left but 2171 is filling fast.
You could apply under 2 different NOCs, but be sure that you do not try to claim the same primary NOC from the same reference letter, because that means they will not be sure which NOC you really worked in. In other words, if you have worked in job A and B, you could apply under 2172 for A and 2171 for B, but don't apply for both NOCs from job A only or from job B only. The exception would be, suppose at job A you spent at least 1 year in role A1 where your duties fit under 2171 and at least 1 year (different time period) in role A2 where your duties fit under 2172, and your reference letter clearly distinguishes that you had two separate roles in two different time periods and specifies the range of time you spent in each role, then you could apply for both NOCs from the same job, but that would be a rare situation.
Your reference letters for both applications should be exactly the same, because there's no telling whether they will compare between your two applications. So if you plan to apply under 2 NOCs make sure you really qualify under both.
Also note that applying under 2 NOCs requires 2 separate and complete applications, each of which contains an original ECA, IELTS, and all necessary documents and forms and separate fee payment.
Good luck.
I agree with everything that you said.. But I do think that there is time for 2171.. Fingers crossed..