aluminum rods vs. titanium rods: fatigue life

iScamp said

2 cylinder air cooled engine for a small amateur built aircraft.
37 h.p. , 3200 rpm redline.
Reducing total aircraft weight even by a pound is a big deal in this application.
These engines are currently built with forged steel rods.

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I would be talking directly to a HP rod mfr. Al-U-minimum has superior lubricity against a steel/iron crank, much more forgiving in any lubrication issue that could arise, but fatgue life is iffy. There are new alloys all the time, and there are Members here that have stated they run them on the street. If chosen I'd discuss a replacement interval as routine maintanance with the mfr.
Titanium is not as light, but is far superior in fatigue strength, however to quote David Vizard..."w/o proper care & lubrication it will weld itself to anything it rubs against, if dry it will stop just short of welding itself to wet ice". Again, there are always alloy developments going on.
Talk to the experts..