I am contemplating to purchase a Manfrotto MA 503 head (my budgetary limit) for use with my XL1s + Sigma 50-500 mm "Bigma". Would this be a good combination?

Thanks for your inputs,

Guus Verheijen

503 seems a bit light for stabilizing the bigma, especially at full zoom....i have a 516 and it's only just enough for big lenses. i'd go bigger, if you can afford it....

Yes, I think a true fluid head like the 516 would be better for a so long range. I've got the 503 too but it's average good for the Sony FX1's zoom, that's all.
Anyway, it's true that the fluid heads are so expensive... and heavy :(