I think the wiggle is just because it's getting hit by lots of wind, it's quite large and heavy too. I took the Midget into work this morning, 35 degrees F, started to put the top on and decided against it, too much hassle. Used the heater for the first time! I was fine with heavy coat and gloves, no hat. Only a 12 mile run or so. Blocker certainly helped. I did get a reflection glare from sun onto the dashboard, minor. Certainly worth playing around with. What a great ride to work though! Certainly adds some spice to life tinkering with cool old cars and using them, got some funny looks, not everyone is cruising around in a 45 year old convertible, top down at 8:30 Sat. morning with frost everywhere.
PS having observed the wiggle in action, I'm going to add two more hold down bolts, the thing rocks a bit front to back. I'll wrap the wood in black vinyl too.