Pece Atanaskovski's gajda drone is pitched at <approximately> Bb on his recordings of pieces like Ovchepolsko oro, Sitna Lisa, Skopska Crnogorka, etc. The Macedonian tambura on these recordings has the lower course match the gajda drone of Bb, with the higher course up a fourth at Eb
In my tambura classes, I normally teach both Macedonian and Bulgarian tambura. Because the top two courses of the Bulgarian tambura are tuned at E (1st course) and B (2nd course) the same as guitar, and many of the people who take my classes have some guitar experience, I transcribe all material at E & B to make life simple, and avoid re-turning.
However, there are some excellent Macedonian tambura teachers (David Bilides and Adam Good), who have standardized on D (1st course) and A (2nd course) for their material. And in an Izvorno Ensemble class, it is easier for gajda and kaval players to read these charts.
So, I will make both versions available so you can pick whatever works best for you.
Hope to see you at the workshop!
ps: and you can always come to my workshops and learn by ear,
if you prefer not to use charts!