There is a lot of "opinion" here that all has merit in an open forum. This is good. It will give you a broad spectrum of ideas and attitudes with which to make your own decision.
Only you can decide what level of safety, comfort, and fuel economy you are willing to accept. However you do "share the road." When you make a safety compromise it is not only you and your family you put at risk, it is also the motoring public and the highway safety folks who have to clean up the mess made on the highway from the "just do it" clan.
Fifth Wheel Weight Calculator
has an awesome calculator that will give you some idea of how much truck pin you will need to carry on whatever you choose. A 15,000 pound camper will require a pin load of 20% plus or minus 5% for safe handling (this is not opinion it is fact easily verified). That is a lot of pin weight for a 3/4 ton SW even at the 15% load factor.
With a 15,000 pound camper you will be safer with a truck capable of handling that load plus your family and "truck stuff" without exceeding ITS maximum gross vehicle weight. Being under the truck's GVW allows you to not only PULL its rated 5th wheel load, but stop it as well. Remember that there is also a maximum combined weight rating to consider; although most likely you will max out the truck before you max out the camper or the combined numbers.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW