I have added llvm + clang + libcxx on Codeblocks. Latest version from svn (cross compiled, it was taking days on the pandora and got fed up). Seems to work well but the PND is not weighting 3.7GB. While I would prefer to let it that way, I'm wondering if the few user of the codeblocks PND would mind the extra size? Or should I go to a separate llvm package (I would prefer to avoid the extra work). So if you use codeblocks you don't want the size increase and don't plan to use clang/llvm anyway, please say so here.
As it stands, people already have trouble downloading the thing through pndmanager (as I recall, I failed last time and downloaded it using curl to my server, then transferred it). It's been estimated there's some 2.0GB limit, perhaps in the download verification code it seems to use (or perhaps it's just transferring it somewhere). Either way, using a simpler tool to download it on a faster machine seems to work more reliably.
So, since you've already exceeded that supposed limit, I'd say don't bother to split right now. If you're ever run out of better things to do you could (if that ever happens) you could split it then. As is, I don't tend to update it at every release because of the faff involved (in fact, since my Pandora is currently rather out of action, I'm not downloading anything at all for it right now).