Fluff Question: Vostroyans

[M@verik115]

Okay so I am starting a new HH project army and I have decided to do Vostroyans. 

Now from the official fluff, they were around during the heresy, but chose not to commit all of their forces in the defense of the Imperium. 
Do we have any fluff regarding how many regiments they did commit though and which theaters they were present in?

[M@verik115]

Never mind I found the answer to my own question. 

Vostroyan's primary purpose was to supply equipment and arms for the Imperial armies, with raising regiments taking a secondary role. 
During the Heresy Vostroya refused to raise further regiments for the Emperor, instead choosing to continue to produce arms and equipment for the Imperial war effort. 
As a result regiments were present, just very uncommon.