Roller Drums for tissue culture; a question of rotation speed
 

I am looking into a piece of lab equipment called a roller drum. How fast
does the drum need to turn for best results?
I have identified two models. The first model, TC-7, has a rotation speed
of 6.0 - 56.0 rpm and the second model, TC-8, has a rotation speed of 0.2 -
3.5 rpm.

http://www.nbsc.com/products/rollerdrums/Default.asp

It seems to me that the spin would not need to be faster than a constant 2
or 3 rotations per minute which sounds about right if the goal is to keep
the tissue in the liquid media from orienting itself to gravity and light
direction. A rotation of 6 times a minute sounds fast to me and a top speed
of 56 rpm must be wrong for this purpose, but I don't know. Does anyone
reading this have any experience that could help me choose correctly?

Thanks,
Al