Why would you want to do this? To get more power connections? That would put a higher load on the UPS than it was designed for so it won't work very well as a UPS. Any good UPS would include surge protection and they help to even out spikes/sags. I don't think any UPS model recommends using a surge protector with their models, and most building safety codes prohibit stringing two surge protectors together which is pretty much what you are doing. At many jobs I had, we would have inspections of the setups and they would make sure we did not have a bunch of things daisy chained. Of course in some training classes our facilities people stuck 3-4 of those things together, so really anything goes till you start a fire.