Framing suggestions

Because I usually work right to the edge of the paper, float mounting the artwork seems the best solution. If this is onto a block as shown below (Illustration 1) I am typically then leaving a fairly narrow margin between the artwork and the moulding, eg 3-4 cms.
Illustration. 1 - artwork float mounted onto a block
float mount framing advice
float mounted artwork
An alternative would be to float mount onto the backing board and then have a window in mountboard, leaving say 1-2 cms before the mountboard cut window, then c.4-5 cms of mountboard in off white.
Illustration. 2 - artwork float mounted onto backing board and then window mounted
framing suggestions 2 k