At 65% and below there is absolutely no reason why you couldn't.
Sunfish what sort of aeroplane doesn't have an EGT?
Just got back from an all nighter in the mighty Boeing...but it was made more pleasant by my latest American Bonanza Society Mthly mag being in my pidgeon hole last night.
Very interesting story about a chap enroute to Oshkosh in his F33A in formation with a bunch of other Bonanzas as part of the huge formation thing they do each year. As he tools along FD&H he suddenly gets a CHT high temp alarm from his all cylinder monitor...looks down and sees one CHT at 410F and heading north at a rate of knots.
He pulls power and enrichens mixture in an attempt to remedy the situation...nothing works so hits NRST APT on his GPS and diverts immediately to an airfield 12nm away and lands safely. Engineers trouble shoot and find a MONUMENTAL crack in the offending cylinder which starts at one spark plug hole and travels through both the inlet and exhaust valve holes all the way to the other spark plug hole and a bit beyond.
He was just minutes away from having that entire cylinder head depart through the cowl followed by a catastrophic engine failure and forced landing. Instead they change the cylinder and a day or so later he is on his way to Oshkosh. At Oshkosh the all cylinder monitor manufacturer downloads and plots the engine data recorded throughout the event and they are able to see it all happening via data points recorded every 6 seconds.
Had he not had a good quality engine monitor he would have never known a thing until it was too late..with possible/probable dire consequences.
How much money did his all cylinder monitor save him?
What does it cost to fix an aeroplane even after a REALLY well executed wheels up forced landing into a paddock...50, 60, 70k?
Instead it cost him labour + parts to change a cylinder and piston.
Even if LOP aint your thing there is plenty of compelling reasons to replace the antiquated junk that passes for engine instrumentation in 95% of the fleet with the latest technology...and it aint even expensive.