An alternative to using the actual +/- physical stab position - which does have a risk of the +/- confusion, or even the "-" sign being dropped from the display, leading to an apparent positive value - is to use a stab "index" rather than values in degrees, with the index chosen such that it is only positive.
In the CRJs, for example, the stab physical travel is +2 to -13 degrees, but the "stab units" value is defined as "2 - stab angle" which results in a value of "0" corresponding to "-2 degrees" and "+15" corresponding to "-13 degrees"; even on the Challenger 600 series, where the range was "0 to -8 degrees" and then "0 to -9 degrees", the "units" concept was used, simply to avoid presenting a negative number with a perceived fear of dropping the minus sign even then. (This may well be a superseded concern, rooted in older display technology)