I recognized immediately what this is referencing and I applaud you for your taste in video game dragons!
Now I'm kind of chuckling at the thought of other artists turning this into an art trend for their own characters...

If it helps any, this doesn't look too bad even with the proportions stretched! It's kind of like CD's artwork or the OVA if anything

Ahh, yes. The common rig transfer troubles I'm all too familiar with myself...

Also: If it helps any, I don't think Crossworlds requires the rigs to be exactly the same proportions when modding. You can probably still make him look good without having to stretch him quite as far!

If it's any consolation...

I used a bunch of empties with "Child of" constraints sourcing from the rig I am translating from, and pressed "Set Inverse" on all of them so I could rotate them individually into the target rig's bones.
After that, it's just a matter of adding rotation constraints on the target rig and baking it.

More progress on the custom 'Outcome Memories' styled Sonic, he's got his legs and shoes now along with some additional changes to his palette, face and quills.
Colors were changed to regular Roblox avatar colors, the brows were reinforced and the back quills were lowered to compliment the head more

Chunky Dragons of any and all forms are not just a want, they are a basic need

An update, now with a custom torso and arms!