All in all, this form seems to be a basal maniraptoran, possibly more
basal, even though the hand is protracted to such a length.
If _Yixiansaurus_ is close to _Sinosauropteryx_ and/or _Coelurus_, then it
would probably lie outside the Maniraptora.
The simple integument makes it unlikely *Yixianosaurus* was a glider,
Might have been a parachuter - perhaps using its dino-fuzz to assist in
descents from trees to the ground.
The leaping-from-tree-to-tree scenario (which many modern primates excel at)
appears to me to be beyond the abilities of non-avian theropods. The
problem is the landing. The hands and feet of arboreal leaping primates are
very good at grasping single-handedly. By contrast, the hands of non-avian
maniraptorans were not capable of an opposable grip. Some near-avian
maniraptorans (e.g., _Microraptor_; _Scansoriopteryx_ - if Czerkas & co. can
be believed) show incipient development of a grasping (perching) pes. Such
taxa might have leaped from branch to branch, but it would have been clumsy
and hazardous, IMHO.