SC Targa Top

The Targa top in my SC was redone about 18 months ago just before I bought the car. However, it doesn't fit too well.
The front is about 1/8" too far forward with the result that the folded sewn edge is a little out of the body recess - not much but enough to bend the edge upwards. The back is about double that -about 1/4" forward of where it should be - and when the top is locked into position, there doesn't appear to be any way of moving it back. For some reason the back edge also turns upwards despite the fact that it doesn't seat snugly where it's supposed to be.
It would fit a lot better if the whole top moved back a bit, say between 1/8" and 1/4".
Does anyone know if there is any way of adjusting the position of the top without re-doing the whole thing?
Thanks for any advice
J