Jeff,

Boy are we lucky ! Oates ( Stephen B. Oates) , in his " Confederate Cavalry West of the River", Published by Univ of Texas, addresses this in his chapter on "The Organization of the Cavalry, 1862" . Oates says that a few months after after Pea Ridge, Van Dorn was ordered to reinforce A.S.Johnston in Mississippi. Special Orders No.52, April 15, 1862 , OR , ser. I, vol VIII, 818 lists the 16 regiments , one battalion and three companies of cavalry that made the river crossing between mid April and mid May . Oates says this action virtually stripped the region ( Trans - Miss) of its best troops . Oates says that McIntosh's old brigade was probably the "best" outfit in the Trans -Miss region. As McIntosh was KIA at Pea Ridge , Col Greer took over command of the brigade and moved them across the river. The four regiments in Greer's brigade were the 3rd, 6th,11th Texas Cav and the 2nd Arkansas Cav. In total , 7,834 Texas Cavalrymen in 10 regiments made the crossing , probably before May 5, 1862. They were as follows; 3rd, 6th, 9th, 10th, 11th, 14th, 16th, 17th, 27th, and 32nd. The remainder of the total mounted group to cross over the river ( total of 11,601 effectives) in the Spring of 1862 was three regiments and one battalion of Arkasas men and three regiments and three companies of Missouri men. A total of 22,000 CSA cavalry and infantry troops made the river crossing by mid May .
As you might expect, the people of Arkansas were not happy abou this because it left them with only a very few Texas and Indian ( Stand Watie,et al ) troops to defend them against a Union army led by Curtis ( victorious at Pea Ridge) .
The Arkansas congressional delegation in Richmond complained directly to President Davis about this matter. They also threatened to pull their Arkansas troops back to Arkansas for home defense . This was not the only state to try this ploy with Davis during his presidency , however, they may have been one of the first. ( Ah , the beauties of a Confedracy built on states rights ) Please, no debates !!!

Given this threat, Davis ordered General P.G.T. Beauregard to begin raising another army in the Arkansas - Missouri area, which he did under Hindman.

Jeff, given this political situation , it is no wonder that the rest of the Texas mounted troops did not cross the river to support the CSA Army in Miss/Tenn. Now , I'm guessing on this but it looks to me like there was some serious "cherry picking " going on as to what troops were pulled across the river first. I mean , it makes sense; If you're A.S. Johnston, you want the "best" troops first . This is for two reasons, one is you want to get these troops integrated into your existing command structure as soon as possible so that you are prepared for action as soon as possible with the least amount of confusion . The second reason for getting these "best" troops across first is that as a commanding officer , you know this massive removal of troops is not going to be popular with the "home folks" ; i.e. Arkansas Governor and Congressional ( which it wasn't) and you suspect that at some point the "home folks " are going to raise enough hell with Richmond to get this action stopped ( which they did). So, this is my guess as to what was going on with the movement of troops.
Now before anyone reading this gets upset about my use of the term "best" troops , I am not trying to slight or dishonor anyone's ancestor. These are Oates' word. I will also say that I believe he bases his assessment on the words and letters of CSA officers who were familiar with the performance ( up to that point) of various regiments. It could have been based on combat performance but also something that is overlooked by many amateur historians (like me , too) today and that is that maybe these first troops that crossed over had better mounts , weapons , ammo , food , clothing and maybe they had leaders who were combat experienced . I mean , if your A.S. Johnson, you would really prefer not to have to provide a lot of supplies to new troops joining your army. You'd like for the first ones joining you to present you with the least logistical / supply/ manpower/leadership problems. All of those things can get factored ( they may not have been) into a decision as to who goes first and goes later.
Jeff, try to look at the Oates book, he really goes into detail about these troop movements and he has great refernces. Good hunting. Craig