I found this beautiful long Multi-Loop spiral from @steven.smitka but it turns out he got the entrance and exit all wrong (as in: not compatible with standard Gravitrax tiles). So I created this simple conversion tile to connect it back to the normal Gravitrax tiles. 

So there are 2 models:

• Multi-Loop fix Base: this one is for the bottom / exit of the Multi-Loop spiral.
• Multi-Loop fix Top: this one is for the top / entrance of the Multi-Loop spiral.

These models aren't perfect and not the most beautiful Gravitrax tiles out there. Maybe when I got time I'll make a better version. Feel free to remix this model (Sorry, the F3D file is a bit of a mess, it was a quick fix job). And if you do remix this, please let me know, I'm curious to see what you came up with!

Huge thanks to @Bas_1189 for providing the F360 files of his Gravitrax high speed curve. It was a great reference to model this conversion model. I really like the separate foot ring, saves a ton of support and make sure you've got a smoot bottom surface. Just a tiny drop of glue and the foot will fit securely in the tile.