I saw Dana dolly at a store here yesterday and looks sturdy and is very smooth. I'm looking at Skaterail slider online and I'm only hearing good things about it. I have read online that Skaterail slider does work on curved tracks, would Dana Dolly work on curved tracks too? I saw that it's wheels can turn but the representative there couldn't tell for sure. Also, can I directly attach the tripod head to Dava Dolly? (Rep said I need to use the ball). I'm looking at carrying either of the ones I buy with me overseas for a shoot. Please suggest which one I should pick. Couple hundred dollar difference will not be a deciding factor.