I use an SPH-4. Not as high tech or comfortable as an HGU-55, but it is more period appropriate for my plane. The retractable visor is nice. Dual visors (gray and clear) is even better. Tinted visor down instead of wearing sunglasses and a ball cap and I was genuinely surprised at how much better visibility was. Like Wes, I mostly use the helmet for airshow...and when the plane comes out of heavy maintenance. (Ya never know, and I should probably wear it more often, like always.) I don't have to worry about the visor knob scratching my plexiglass, but my cockpit isn't as tight as yours, so be sure you have the clearance you need.
Good luck!