I concluded that with RH-34, Ralf Heim was seeking to further elucidate the QSAR of the NBOMe class. The key takeaway is that the O-methoxy is a requirement (it also overlays the O in the amide of LSD and the lone-pair is in exactly the same orientation), an aromatic (he used benzene and thiophene for those) which I suggest is space-filling a methylene spacer and then a secondary amine and it's lone-pair also overlay the 8-nitrogen of LSD.
So he placed his NBOMe group onto the nitrogen of ring-substituted PEAS (and semi-rigid derivatives such as TCB-2), onto various tryptamines and onto other 5HT2a modulators such as quinazoline-2,4(1H,3H)-dione, a relative of kanaserin.
It seems that the NBOMe modification is only capable of producing partial agonist activity which is interesting.
He and Nichols worked together and now Ralf Heim is working with Nichols. DMBMPP seems to re-enforce the fact that secondary amines are optimal.
It's the biggest step forward in the research of 5HT2a ligands for decades. There is no shortage of other scaffolds the NBOMe modification can be added to but Rale Heim is in the right place. There is decades of work ahead and given his style of development, it will be slow but finely granular.
The fact that know, tested and understood 4HT2 agonists were chosen resulted in the tryptamines and the ring-substituted PEAs, I don't think that the work was primarily aimed at developing a new class of hallucinogen. It's just that you can train an animal to respond to, say 2CB, that's been done, so you can test the NBOMes to see if the subjective effects are the same. Convenience really.