I have had them go through the prop and appear out the other side unsplattered and that was a 4 blade job, well it appeared to go through it
Also they can come in round the prop.
As for the cap ?
Would have thought because of the pressure increase inside the hull alot of the wind will get put over the top.
I got made to open our DV window below 140knts by a TRE and there was remarkably little wind blast.