That camper appears to have a storage or generator compartment, so I don’t think it will slide forward.
There are a few people here running short bed campers on long beds. It’s basically the same distance to the axle from the end of the bed on short bed and long beds. It can be a few inches different. Handling wise, it mostly should be ok.
If it is a great deal, you could always try it for a while and if you don’t like it, trade for a long bed camper.