Reference letter format for multiple positions at the same company

Here is my situation:

I have worked at the same company since 2015, but with different position titles. Additionally, I was on contract initially, and then became full time permanent employee. Although, from the perspective of NOC, I have done the same work, and have been undertaking the same responsibilities.

Now, my manager is generous enough to offer me to write a reference letter however way I want.

Give my above situation, I have come up with the following structure:

==========

To Whom…

This is to certify that Mr. XYZ has been employed at company XYZ as a XYZ. He has been working on XYZ product of the company. The following lists the positions held by Mr. XYZ:

Month 2017 - present
Position Title, Full time, parmanent

Month 2016 - Month 2017
Position Title, Full time, on contract

… more positions

The following lists the responsibilities:

End paragraph.

Signature

==============================

Is this letter structure ok? Or does it look unconventional? The breaking down of different positions, the way I have done – is that going to attract undue attention from the visa officer? I can substantiate positions with payslips and tax return proofs, so no problems there.

Thanks.