The high compression 205hp 370 and the (unknown) advanced timing are a dangerous combo IMO.
With a timing advance map based on manifold pressure and RPM, theory says a variable advance system will not command advance excessive enough to grenade the engine, at least if kept plenty rich or plenty lean. I say "theory" because we've already noted a Lightspeed goes to full advance with a failed manifold sensor, and high compression does narrow the margins.
I too dislike unknown timing schedules.
I run the same engine and the only EI I would consider would be the CPI as you can control the advance curve.
IIRC, it is the engine Nigel flew for a complete survey of timing, speed, vs CHT, for two mixtures, as reported in Kitplanes:
Download here with permission of the author:
https://www.danhorton.net/Misc/Nigel Speedy - Ignition Advance .pdf
Fair summary...CHT rise at 100 ROP averages 2.5 F for each degrees of additional advance. CHT rise at 25 LOP averages 1.5 F per degree of additional advance. The optimum advance setting for ROP and LOP are
not the same. ROP was optimized with only 3 degrees of additional advance. LOP required far more advance for best speed, but in general, only when up high.
Here's the Catch 22. Climb requires power. More power means more rate of climb. Best power is found running mixture ROP. With a single variable schedule optimized for LOP, timing will advance as the aircraft climbs and manifold pressure drops with altitude. CHT will rise at 2.5 F per degree of advance,
compounded by the drop in air density (i.e. less cooling mass flow), so the engine gets hot.
Put another way, lots of advance might be desirable with a parallel valve after the aircraft gets to some upper altitude and can set LOP... but the poor bugger has a tough time getting there.
SDS CPI and EDIS/Megajolt both offer dual maps, the ability to program and switch between two different advance schedules, i.e one for ROP and one of LOP. A Lightspeed can be wired to bias timing plus or minus 5 degrees from the pre-set timing schedule. Surefly offers the ability to set fixed or variable timing, which only requires the user to think about his mission.
Personal opinion, but if the mission is mostly fun flying at lower altitudes, there is little value in variable advance. A Surefly set for fixed timing is a fine choice for that application. The user stills nets all the start and idle advantages, can run very, very lean when desired, and can climb at will without driving CHT to the top of the scale. It's not ultimate performance, but it is easy on the machine.