Ultra Cable in a full bed is, in my experience, the most notch resistant string I have tried. Twice the durability of any other full bed poly string.
Tension loss may be an issue with this string and particularly in such an open pattern. However, I strung it up in a 16x19, 112 square inch racquet at something like 57/53 and it still is fine after the tension loss of about ten hours of hard hitting play. I definitely notice a change but it hasn't affected my game all that much. You'll have to try it to see how it works for you.
Yup, it seems to be the case with spin racquets. They tend to lack control especially if a player has flat strokes and they eat strings like crazy which encourages players to put stiffer strings in them. I then usually get an ensuing request for a softer setup followed by a request for longer playability.... etc.... etc... etc...
For polyesters to resist notching, pair it with any softer poly or co-poly. Softer polys or co-polys are touted by their manufacturers as GENERALLY being softer [not always true] and SOMETIMES better able to resist tension loss. The softest string class IME that will not notch poly mains are always SG or coated multifibers. NG will also work. The best SG is a low string COF one such as Bab SG aka SpiralTek. If one insists on using poly/poly hybrids, the cross should also be round and SOMETIMES smaller diameter. 4G/4GS/RPM Team would be good mains. 4G or 4G Soft are not good candidates as non-notching crosses due to their hardness. ZX or PEEK is in its own class. It is soft, holds tension well if pre-stretched and will notch poly. ZX mains is something I have never run across because none of my poly clients use it due to its softness. IIRC, I had one, but it broke quickly due to a mishit. [Never More said the Raven]
Stiffness rating does not necessarily translate to the string being harder to grind as well, in order for the poly hybrid to work you need a cross string that is soft enough to get thinned out flat by the main sliding on it, and the main hard enough that the cross does not eat thru it.
My favorite cross is Ghostwire, but I have strung for a solid 4.0 Babolat RPM as mains and broke the mains full cut thru, then Black Knight and it outlasted the cross but still got worn half way thru, and so far the best (as far as longevity and playability) has been Spiky Shark as a main with no damage done by the cross.
-lets be clear though
-ALL strings notch EVENTUALLY!, specially if crossed with another much harder string
-i find that some of the crisper slick polys tend to hold up best, IME
-hybrid string combos will mitigate the notching in different ways,
-the softer string will/should break down first, (generally speaking and definitely more so overtime)