It's difficult to determine the length of the garment. The VMS guy is short-statured. Look at the size of his head in proportion to the rest of his body.
The tunic in your example to the left looks a little too fancy to me. I see the Gemini tunic as more similar to this one in Tacuinum Sanitatus (with allowances for the fact that VMS Gemini has much shorter legs and might even represent someone with dwarf stature):
Or, if you want a longer tunic, since it's difficult to picture how the Gemini tunic would look on a taller-statured person, this one (the simple one on the left) from c. 1500 Flanders:
The tunic in your example to the left looks a little too fancy to me. I see the Gemini tunic as more similar to this one in Tacuinum Sanitatus (with allowances for the fact that VMS Gemini has much shorter legs and might even represent someone with dwarf stature):
Or, if you want a longer tunic, since it's difficult to picture how the Gemini tunic would look on a taller-statured person, this one (the simple one on the left) from c. 1500 Flanders: