"Having been away from racing and serious training for several years, I'm running an old MTB crankset (110mm BCD) with a 34T single + a chain guard (cut from a 46T ring). I have precious few times when I run out of gears on the high end.…"
"110mm BCD (Traditional MTB Standard and new Road Compact Standard) will accept a minimum of a 34T ring. 50T is about the largest big ring that you'd want to use, but for 'cross, I'd recommend a 44T, 46T or 48T."
I didn't even list my wife's Cannondale MTB & road!!
My first "serious" bike was a Cannondale in 1988 (replete with decal-matching yellow stem, handlebars, cable housings and saddle) and I've been a dedicated fan ever since.