RE: Kress Jets HE-162 Salamander
Interesting build.
I don't know anything about Kress fans so I can't comment. You might want to pose the question at RCGroups, EDF forum. If it were mine, I'd forget the Kress fan and buy a current design fan with the appropriate motor and ECS.
"...I don't like hand launching much, or using a catapult of some type. This model will not have landing gear. Would a dolly that drops during take-off be feasable? ..."
Launch dollies are tough to do right, at least for me. If the dollie relies on the plane for motive power, the fan may or may not produce enough thrust to achieve take off velocity.
Assuming the dollie/plane system will reach TO velocity, you then have the problem of keeping the plane on the dollie until it is ready to launch. If the plane leaves the dollie before stall speed is exceeded, it will merely roll to one side and crash. So you need a mechanism of some sort to insure the plane remains firmly attached to the dollie during the TO run.
This becomes even a greater issue if you are trying to launch from grass. The dollie will require its own battery, receiver and steering servo.
I have seen a powered launch dollie based on the chassis of an R/C truck, which you probably have. This option will insure TO velocity is reached and is steerable. The problem of keeping the plane on the dollie is the same as the un-powered version.
Consider using an dollie mounted electro-magnet to keep the plane on the cart. You could control the magnet current from an unused channel of your radio.
After all is said and done, I think a bungee is the easiest with the best chance of a successful launch.