Sure you can make it hold with epoxy.The thing is ,if it was polystyrene it would be easier ,but those cones are a type of polypropylene a much different animal.
First thing is clean,clean and clean.Before you do ANY cutting or sanding of the part,take it to the sink and wash it with dish soap and hot water ,rinse and dry and wash again.The NC will have traces of release agent on it ,so if you sand before you wash ,you scrub it into the plastic and there it stays ,making proper glue adhesion impossible.
After it`s dry ,take yourself some isopropyl alcohol and wash the part down again and then wipe dry with paper towel.
Since the epoxy will not be absorbed into the plastic ,your epoxy joint will be solely mechanical (although it will bond to and into the wood CRs)so you want the roughest surface you can get or even better angled cuts.
Take you some 60 -80 grit sandpaper and give the areas to be bonded a good scrub ,but alternate the direction....criss cross pattern.
Now grab an Xacto knife or similar utensil and cut/score deep gouges into the plastic ,again in the area of bonding....use a cross hatch pattern and keep the cuts about an 1/8" or less apart.All these deep cuts will allow the epoxy to "KEY" into plastic and form your bond.
After you are done with the sanding and cutting ,wash the area again with alcohol.Alcohol is great as it dries/evaporates quickly ,cuts oil & grease and leaves no residue behind.
Now you are ready to apply your epoxy (15 minute may be a good start....30 may be too thin and not build up enough)
Apply it thickly and use plenty on both sides of the CRs ,to lock them in on both sides.
I`ve done this many times and it works quite well ,but it`s all in the preperation.
Ahhhh geeze.....I`m too slow.....I`m always last !
Paul T