Gil,
I have applied iron on over fiber glass with success but there are some cautions........

Use as little heat as possible so as not to warp the glass part or to soften the resin, also if you get the iron on covering too hot it will gas off badly and cause lots of bubbles between the glass and covering.  The gas has no place to go unless you prick the covering:(

Then the problem of sealing the edges........
Not sure exactly what you project involves but you must seal the edges of the covering to keep fuel etc. from creeping under the covering since it's almost impossible to get the covering to follow the weave of the glass, if any weave is visible.

Have fun:)

That should be pretty easy.......let us know how it works out.

Which iron on are you using?