HI THERE

i have had 55x in three different airplanes; it works well and is relatively reliable.

the back lit display tends to fail; which does not effect operation, just the ease of viewing.

but why?

the whole Stec system is a small fortune,

MAYBE
           you use the servos and the installation from the "30"? that would mitigate a great majority of the conversion costs. just don't need too much from Stec.
and a "minor" repair at Stec cost $1,420 and a major costs about $2,400 but if you want it in a timely fashion that is another $400

what about going to the Dynon or the Garmin for experimentals. you get a whole lot of value and the cost is in the $5,000 to 8,000 range, and that is for everything that drives the autopilot
                       AND you have a brand new glass screen display

and this from someone, me, who has a yellow tag 55x panel unit for sale

peter

by the by
when Stec was approached by a dealer with a major multy unit order, Stec would not sell  install packages without the panel unit. OH, they would sell it at list price for all the separate pieces, thus making the cost saving non existent