Late Roman Army Grade/Rank List under Anastasius

[Longovicium]

However, if we play a game here and use the 50 veredarii as a separate cavalry type (following Pavkovic - perhaps armoured horse-archers?) and attach it to the first century we have 225 veredarii troopers remaining which splits nicely into 9 cavalry turma of 25 troopers.
 
A squadron of 25 troopers has extremely limited deployment arrangements, like 5 horses wide by 5 horses deep. How does it extend its frontage and depth evenly if required? What is its frontage in column of march?

 The Anonymous writer circa 550 AD discusses cavalry arrangements at section 17: There is the file leader, four ranks behind him, the rear and flank guards, all brave, physically strong and with combat experience. The horses are deployed differently to reduce or enlarge the squadron - some line up the heads of the horses of the second rank with the shoulders of the front rank, others line them up with the flanks of the horses in the front rank. Depth is not such an issue with cavalry squadrons as unlike infantry formations horses cannot 'push' or 'brace' into the body in front. The cavalry phalanx differs from the infantry one in that it possess mass and speed at the charge hence it does not require the push and density which infantry phalanxes need.

I think Mauricius writing a little later goes into more detail regarding this issue.
 
Several turmae together would form up in line abreast or in column/wedge formation. As with the infantry, each trooper would be designated as a primani and secundani (the Anonymous writer calls then protostates and epistates respectively) down the file. Using that convention will allow the turma commander to open the ranks or close them up.

Frontage? No idea.