Unfortunately, I cannot answer this question right now. In fact, no one really can, as there had been no research done on this subject. Even traditional sources (i.e. Talmud Bavli, Menachoth 28b) not sure about even approximate dimensions of the Menorah and its parts and provide only approximate and rather speculative information.
However, logic dictates that the Menorah would have to be relatively tall so that its Lamps would not shine directly into the eyes of the priests serving in the Tent of the Tabernacle. This would mean that the height of the Menorah would have to be at least 4-5 cubits.
Also, as Exodus 25:37 and Numbers 8:2-3 specify, Lamps of the Menorah would have to, at least, illuminate the Table, especially when the priest would be standing right by it. This means that the branches spread of the Menorah would have to be about 4 cubits (wide), so as to provide maximum coverage of a 2 cubit wide Table from ~5-6 cubits away, while still allowing Menorah to stand vertically and not to fall down due to its weight imbalance.
Thus, the Menorah would look somewhat like so: