ok ive checked with the search abit and didnt find much but my main Question is do all Sun unis have the same seat post diameter and seat bolt on way??? also wats a comfy good seat upgrade for a 24 inch sun uni with a good pull up spot in the front?? plz help 
what type of riding do you do? freestyle, flatland, trials, street, muni, distance?
The consensus seems to be that they use 22.2mm as their seatpost diameter.Here is another 22.2 mm diameter reference with JC as a contributor which makes it pretty much gospel. This was (is) a unicycle standard for some time. It’s not necessarily good or strong but it’s easy to get. If it will accept a standard United style saddle bolt pattern is the most universal also. This should accept a KH, Viscount, United, and several other saddle brands. The KH will be the most comfy of these. It is also the only one I know of with a front handle.