Salvete,
I have a first century spatha with a blade length of 69.5cm and is worn on the right, from a baldric. I have no problem whatsoever in drawing the blade from the right hand side.
There are depictions of soldiers (auxiliary) frrom the early second century wearing their swords on the left. Namely on the Adamklissi metopes and one particular scene on Trajan's Column. So we could be seeing the first movement from right to left during the Trajanic campaigns in Dacia.
Here... Adamklissi metopes, Mail shirts, oval shields, scabbards on the left.
http://i20.photobucket.com/albums/b242/ ... /met-g.jpg
There are many scenes of cavalrymen wearing their swords on the left on this monument too. This would make more practical sense. When you are wielding a hasta or lance the sword would be well out of the way of your weapon arm hanging on the left.
The scabbard on the Adamklissi metopes is also slung VERY high, almost under the armpit. This is also depicted on the cavalry troops on the Hadrianic friezes of the Arch of Constantine.
If your sword hangs too low, it will smack the rump of the horse in effect 'geeing-it-up'. If you are pulling up on the reins to slow the horse down, the animal sometimes gets confused, as it is still being tapped on the backside by the scabbard, making it think it should go faster! Having the sword tucked up under the ‘static’ left arm holding the shield stops this happening, and holds the scabbard very firmly out of the way.
And here... Trajan's Column, auxiliaries defending a fort from a Dacian attack. All visible baldric's are on the right shoulder.
http://i20.photobucket.com/albums/b242/ ... heleft.jpg
(And I did wonder if the images were reproduced the wrong way round, but the men clearly have their shields in their left hands)
Regards,