Oh, I'm glad you're up and running, deedum! These little things will drive you crazy sometimes, won't they?
Debbie B, if the speed of your 15 is overwhelming, you can solve it with a variable speed router control - about $20 at Harbor Freight.
You put the router controller between the machine and the outlet, dial the variable control all the way down, then run your machine with the foot control fully depressed.
Slowly turn up the variable speed dial on the router control until your machine is running as fast as you want to sew and you're good to go. This really helped me a lot when I was trying to learn on a jackrabbit machine.
For an even better solution, switch to an electronic foot control - it's much more sensitive than the old bakelite button style controllers that Singer used on most of their machines. The electronic foot control takes about five minutes to install in place of the button controller.
You'll be amazed at how much less fatiguing it is for your leg and foot muscles and how much easier it is to run the machine at a steady speed. :)