I agree it's too big! I'm going with it anyway though. Yeah 6DC, 4++ though the added toughness of having an invulnerable save. It doesn't seem unreasonable that tyranids would breed bio-titans around the size of Warlord titans for planet's they're meeting strong resistance on. I'm doing it for the looks and aiming more for best army painting prizes at tournaments than getting gaming advantage to win them (at best I've come mid table at tournaments and come last at a few). I'm unsure if larger size is overall an advantage of disadvantage in game? It can cover more ground and I can position objectives spread a distance apart where it can capture both but a 60mm based titan wouldn't. On the flip side it makes it harder to hide behind smaller pieces of terrain and so they'll get shot more.
I was originally going to base it on the 90 by 120mmm oval base the Tyrannofex comes with and I'm using for the Dominatrixes. The front pair of legs would have to be posed going mostly forwards then and I really wanted to have the model posed more like the old epic model with those legs going sideways as per this:
One outstanding bit I haven't decided what to use for yet - anyone got any suggestions what to use as the tail end? I've cut the tail part way down and am going to repose it so it curls inwards like on the old model, but ideally I'd like a modern part akin to the most of a circle cutting blade like the old model. There are various tail ends on 40k tyranid models I could use but I haven't found a good match yet.