Hi
I made a carbon front fender for my Husqvarna 701 Supermoto in a four part mould. The part of the mold that depicts the assembly area is cast from polyurethane.
 
I fill the mounting area of the front fender with a thickened resin before vacuuming.
I use about ¾ teaspoon chopped carbon fibre strands on 65 g of resin.

The result looks neat, but the assembly area is more brittle than I expected.
It sometimes breaks when I drill it. I am afraid it will break in rough use.
If possible, I do not want to build a new mould.
Any suggestions?
Regards
Frank

What george said is probily the easiest an best idea
With composites you design the part for your material not copy your part in your chosen material.
Not perfect but if you did want it in one operation,no bonding additional bracket,split your mould through that feature. 
With the two parts of the mould One ply front an rear rear both running into the feature.
Put localised reinforcements in the feature to fill it
Bolt mould together an do the rest of your plies as whole plies for the complete item