As a simple and easy to write format, we use SRF point clouds. SRF is an ASCII format, with chunks of 9 floats (x y z nx ny nz r g b). SRF might have a global surfel radius information at the begining of the file: (e.g. #1.2 at the first).
I am currently re-implementing this plugin with new and more robust features for PointShop 3D 2.0 (the release below is for PointShop 3D 1.2 only).