The comparison to the R-Pro Rhyno may be a little hyperbolized, but not by much (I could have also gotten a straighter Rhyno, my sample size is 1 haha). My K1s remind me of a fresh JK-Aviar or a Wizard in stability. I'm definitely going to keep giving my K3s a try since I'm admittedly not the most consistent player, but I just found if I tried to power them up or down, they act differently than I expect them to.I would suggest the Orion LF in Millenium Standard plastic vs a Pro Thunderbird. Orion LF has a bit more glide and a bit straighter with a nice drifty finish, probably between a standard Thunderbird and Valkyrie. Thunderbirds need a little beating in before the glide kicks in.
My K1 Rekos are dead straight (with a slight finish if I give them height), and the K3s fly a little more OS, but beat in faster. I think you may have gotten a mutant for your premium plastic Reko.
A K1 Svea might be a good slightly US mid for you if you don't mind dome (dome is king). The svea has been compared to a Fuse in the past. Also if you pick up a K3, they get real US and can do some hard turnovers that you don't want to fade out. K3 is my US utility disc.
I was also wondering if anyone would recommend the OLF since I know it's a fan favorite and gets a lot of love on DGCR. Isn't the standard like a DX type plastic? I know it's baseline, but not sure if their baseline is more the DX type plastic or the i-blend/pro type plastic.