[hharney]

Other than the proprietary increase that Air Scan did the only increase I am aware of is Robertson STOL. This was an increase gross weight for take off but defaulted back to certified gross weight for landing. It's a lot more work and money to change the weight for landing than it is for take off. VG's on the Skymaster did not gain any GW like a lot of other twins benefit with. There are some early (pre 73) Turbo models that have R-STOL but very few later model Skymaster had the R-STOL. It's cost prohibited to install an R-STOL system today, even if Sierra would do it. The P models are heavy birds and will work pretty good for 2 adults and gear with long range fuel but for 4 adults the fuel load is going to be compromised.