I agree with you on wanting a twin. At least three times in my 500 or so flights on 33-35% twin engine aircraft, I've had a cylinder go out for one
reason or another. Each time I've been hovering. With a single I would've been out 4 grand with each outage. Just from a reliability perspective I
like the twin -- $12K savings for motors that cost $5-600 more.
One of the times a plug cap went out. If one went out on a single, thud. On one a spark plug broke due to vibration as a firewall was pulling loose, and on one a plug cap came off. Each time the engine had enough remaining power to pull out of the hover on a single cylinder.

On the prop compression issue -- it's even more of a problem with 6 bolt hubs. With a single bolt hub if a prop bolt comes loose, the prop spins. The engine dies and you may or may not lose your spinner cone.
On a 6 bolt hub if the prop comes loose, the engine will shear off all 6 bolts. Yes I've seen this happen. You lose the prop, the bolts, the spinner, and maybe the aircraft if losing all that sets your CG too far back to land.

Also, the choice of prop has a lot to do with this. Menz props tend to compress just a tad over the first 10-20 flights. With either a 1 or 6 bolt hub, tighten after every flight then every other flight for awhile. Once the Menz is done compressing, you will barely able to see the indentation in the wood.
I've seen some other wood props (sorry, I don't remember the brand) that will compress and compress and compress forever until eventually the prop washer works it's way so far in you can no longer tighten the prop nut (it's below the surface of the prop!)