For comparison, here he is next to Siam. (I felt awful turning them over for the picture, but it was a split second

I'm worried now that it may be too crowded because my tat is only a 40g. With five crabs of all different sizes, I'm worried for the larger crabs as they approach the "jumbo" size.
Koa is due to come up soon too if he's molted again, and I know if Ozark has gotten this huge, Koa has gotten even bigger. Koa was always the largest of the five.
With all of that being said, Should I move the two small crabs to another tank when possible, or will it be fine for the large crabs because of the small size of my other crabs?
We do not have much room for a larger tank, which is why separation is what I'm looking at.
All in all, I'm trying to give the best care to all of my crabs and assure that they're thriving in the best conditions I can give, as all of you are!

If I do have to separate them, how would you all recommend I do so?
Notes:
-Koa will possibly be in a 1 1/2" - 2" shell if he has molted again, as well as Moja.
-Koa, Moja, and Ozark are my three large crabs.
-Siam and Chella are around the same size, but Chella probably is a weeeee bit bigger..

5 PPs: Koa, Moja, Siam, Chella, and Ozark