I make my own spinners too and here's a couple of things you can try that I've found through the years I've been making them:
For the Mepps style spinners: I'm attaching photo's from the
Canadian Guide to lure making as you can't draw pictures here
http://www.luremaking.com/howto/frenchspinner.htm
You should be working on the bottom of the spinner FIRST,
http://www.luremaking.com/howto/images/frspnstep1.jpg
make your loop put the hook on and then you want to take your brass or silver body and slide it down the wire then squeeze the wires together and run the body weight over both.
http://www.luremaking.com/howto/images/frspnstep2.jpg
Holding the spinner body, take the tag end bend it over and snip it and your body weight is attached. This step right here is where you might be bending the main shaft a little that's why I say to make sure and hold the weight when doing this step.
Now put on your beads and clevis and blade
http://www.luremaking.com/howto/images/frspnstep3.jpg
Then make your closing loop for attaching to your line
http://www.luremaking.com/howto/images/frspnstep6.jpg
A word about the spinner clevis!!!!!! The stirrup clevis's are ok but I much prefer the folded clevis's they seem to spin better.
One reason I can think of why your spinners aren't spinning at slower speeds is your blade size ratio to your body weight is off. Download their lure making guide and on Pg. 25 is a chart on In-line spinners and blade size to body weight style, you'll have to print off a copy of the page from the catalouge to show body style to match against the guide below
http://www.luremaking.com/catalogue/download_guide.htm
The other problem I can think of is your eye for tying to your line is off center of the main shaft of the spinner. To try and adjust this try bending the eye one side or the other of the main shaft cast out and try to retrieve at slow speed and see if that will fix it. If not bend the other way and try again. This could be the same problem your having with the Panther Martin style spinner too.
I've never bought a kit, I just buy the coils of wire and all the other components. If you don't have a wire forming tool this can be tough to make them.
That's about all I can give you for help, let us know how it works.
Fatman