Ventist
I have tried the Ventisit pad on an Optima Baron (not mine) and it is very comfortable, provides noticable ventilation and offers a bit of a suspended feel. The Ventisit works well on a one-piece recumbent seat because of the relaxed curvature and it is easily held in place with some adhesive carpet tape or Velcro tape.
While I have no experience with a Ventisit on a Sofrider, the only issue I can think of is that the seat of the Sofrider (as well as the other models of Cruzbikes) is a two-piece seat with a distinct seat pan and back. This configuration requires the Ventisit pad to bend at a rather sharp angle and would not likely be held in place with Velco or tape alone. I have seen in this forum a rider who has fitted the Ventisit to a Cruzbike, and the picture celarly shows zip-ties anchoring the pad to the seat pan. It's not a bad solution, just one to be wary of.
The beauty of the Cruzbike seat pads is that they are light and can quickly be removed if you fear your bike will get caught in the rain. However, if you must be on the bike in the rain, the seat pads are still quite necessary to keep in place, right? ;-) With that said, if it's raining, they will get wet.
If this is a concern of yours, another option is a Zotefoams seat pad. If you can get your hands on the material, it's not too difficult to make your own. Take a look if you're interested. This will get you pointed in the right direction:
http://www.recumbentriders.org/forums/showthread.php?t=3961 (Opens in a new window)