Shawn: The lack of records for the Guard makes it impossible to do more than estimate its strength.
As an example, I have done extensive research on the 1st Division. By examining the available muster rolls, discharge records, county histories, memoirs, etc., etc., I have compiled a roster of over 3600 men. However, records for the better part of 3 regiments of infantry, and 1 regiment of cavalry, and 1 battery are nonexistent. Based on the average enlistments in the units with records, I estimate that the 1st Division contained at least 5000 men over the course of its 6 month enlistment.
Gen. M. Jeff Thompson, the 1st Division commander, reported in his memoirs that he never commanded over 4000 men in 1861. I suggest that he was mistaken, or else the missing muster rolls must contain miniature companies.
There is a gentleman working on compiling a list of all Guardsmen that he can identify from every type of record available. The last time I communicated with him he had over 15,000 names and still counting.
Based upon the number of units in the Guard, I think that probably well over 20,000 men enrolled at one time or another during 1861-1862, but there is no way in the world I can ever hope to prove that number. The records simply aren't there.