NO, absolutely not.
In no circumstances must this be attempted by yourself or serious injury may occur.

Once a Made to Measure Glass item has been toughened it cannot be altered; it will explode if you or anyone else, including us, attempt to drill or cut the item down.
If your item is binding slightly we may be able to grind down the edge of toughened glass by 1mm or so but even that may cause the glass to explode.

So please remember the saying, "Measure Twice, Cut Once."