The chamaedorea that can take the most sun is plumosa, but it is solitary, not suckering, though the height would fit your needs.

Have you considered Dypsis lutescens? My understanding is it's commonly used for screening in Florida, grows very well there, is suckering or clumping, and fits your height requirements. Also relatively inexpensive and readily available.

Hi here is a link that may help check it out ....

Here is a link that might be useful: http://www.junglemusic.net/palms/

I sometimes think reading various sites and descriptions of various palms on various web sites, that some folks call any palm a "clumping" palm , when two or more are planted close togehter , whether they produce offsets to be natural clumpers or are just planted that way intentionally. At any rate I sometimes wonder how long those clumpers take to grow a very nice clump from a single plant , from the time the first one is planted?? The reason I ask , is because I'm thinking of starting a Rhapis multifida in a container , but do want it to fill out quickly, or would it be wiser to plant two or more from the beginning for a fuller look?

Needle palm would be a good choice I would think.