"Official" grade conversion is skewed at my disadvantage, how to proceed? I am a Master's student in Italy, and I'm applying for a thesis internship in a lab in the US. To this end, I'm required to send my Master's transcript as well as my Bachelor's; however, in the case of the latter i have a problem with grade conversion. 

My institute offers a supplement that is meant to convert grades to their ECTS equivalent (A to E scale, similar to the American one with one additional step); however, they do so by grading on a curve even when the original courses weren't. As I followed a program with an unusual concentration of high-achievers, my (not distinguished, but acceptable) grades average is strongly shifted downwards according to this system (think a hard C instead of B+), yet in Italian grades it's higher than the institute-wise average for Bachelor's degrees (26.0/30 vs 24.3/30).

The absurdity of this system is evidenced by the fact that, for the same exact course and exam , the ECTS grade calculated with this system widely varies according to the different program overall averages, resulting in Italian grades lower than mine translating for other programs in ECTS grades higher than mine.

Regarding my application, I believe this leaves me with a few options:


Not doing anything, and expecting the person in charge of scrutinizing the transcripts to understand that a system translating a 30/30 score as a B is far from perfect
Attaching a note to the transcript explaining what i explained here
Supplying my own transcript with only Italian grades and letting them figure that out; maybe also attach a reasonable suggestion for conversion, like the ones evidenced in the answers to this question


Does anyone have suggestions on the best course of action?
As someone who spent several years working in university admissions in the UK, I would suggest that you supply just your Italian transcript to the US university and let them figure out the grade conversions on their own. The US institution should have access to international grade conversion guidelines so it's likely that they'll convert your grades more reasonably than your own university has. 

You might want to consider attaching an official English translation from a professional translation company so they can read the course titles etc. in English. Where I worked, we always asked for official translations in English but never for ECTS equivalents. 

You can supply them with the supplement (and an explanation) later if they ask specifically for that.