Hobby Club is selling the CS 28 imported from China.   I picked one up for $50 plus postage.   I havent run it yet but am overall impressed with the design as far as looks and the potential as a sport engine.   Here is the plus and minus list.    On the plus side all the castings look really good.   I dont have a digital scale so havent weighed it but it is very close to the OS 25 in weight.   The muffler is light for a relatively long (maybe even half wave tuned pipe long) one piece assembly.   On the minus list it came with the piston frozen at top center.   About 15 minutes in the oven at the lowest setting (about 180 degrees) and it turned over easily.  The prop nut appeared to have been put on with a power tool of some kind and I could not get it loose until I put a bamboo dowel into the exaust and took a wrench to the nut.  Once the nut was loose I noticed that it has a bit of wobble on the shaft, almost like the nuts I picked up for wing tip weight from a tractor supply company... it should work but I'll have to avoid over tightening it.   The RC carb seems to work freely but the parts are loosely fit together and I suspect getting a good consistant slow speed setting might be a challenge.   Since we run most CL engines at a fixed setting it should work fine for us.    The only really interesting issue that might be fine when the engine is running is that the cylinder is tapered (good for high performance engines) and when you look into the engine you can still see the tooling marks.  Again I havent run the engine so this all could be a non issue but I'll post something one I know.  Gret price but you do get what you pay for...
Bob