Or the weight... Seriously, that thing would have to be hecka strong, especially to be eight-legged and presumably have some ornamental features (3 heads, carvings, etc)...
That said, it's a wildly cool idea, if it was just a bit shorter. Even the Titan in Maos is only a few thousand feet tall, if I understand it correctly. And that's using Shintouite, which explicitly works better the more pressure it's in.