I use the latest Beta of 4.9 and 4.9 side by side with little issue. It gives me the functionality of two versions of Studio with all of the latest compatibility and functions. I can't really see any advantage of running 4.9 and 4.5 side by side other than personal preference. I'm honestly glad that DS product development isn't focused on keeping old version functionality as core. A stance that successfully drives innovation and progress within the platform and content. Sure keep old content functionality with new platform versions. But restricting new content to old version capability, because of a fractured market, is in fact more of a ball and chain then anything positive.

As far as DSON/Poser issues go it's really the thin edge of a wedge of changes that began a long time ago now. SM made it clear that there position was not to optimise Poser to increase support for third party development, this is the ultimate realisation of that stance. The choice of 3rd party developers to not hamstring their own content development or security simply to fit Poser compatibility is an extension of that same concept initiated by SM. That was the point that SM chose to dig its heels in and say you either chose to create content for Poser or you're on your own with your content. Unfortunately Poser users are now experiencing the other side of that double edged blade of a decision by SM. A fact that numerous people pointed out at the time, only to be branded derogatively as "Daz Fanboys". It makes you wonder if at that point SM had chosen a policy of collaboration with the largest content provider in the market, instead of taking a high ground stance that was ultimately aimed at keeping content developers bound to SM and Poser support, if things would've/could've worked out differently and we could now be dealing with a much more collaborative relationship between the two platforms and by extension much more healthy satellite communities in general.

SM chose to restrict Daz 3D content from its own platform for its own benefit and business interests, which many Poser users cheered on as a good move at the time. It's ironic what Poser users now say when Daz 3D has essentially done that very same thing instigated by SM. Made changes to their own content and platform in disregard to third party platforms or consumers of that platform. The DSON/Encryption compatibility issue with Poser is not actually a Daz 3D issue but the realisation of policy stance made by Poser developers, which could possibly leave Poser faithfuls starving for content in the long term. Daz 3D has treated Poser users in a manner no different than SM, who, if anyone, has an obligation and responsibility to that user base.