It's early days with Scaler 3.3 but I have had no crashes with it in FSP yet and earlier versions of Scaler 3 were OK for me too.
The one thing I never do with Scaler is host VSTs inside it. I just use the built-in instruments for roughing stuff out then route the MIDI to FSP tracks for the "proper" version.
In the early days of Scaler 3 there were loads of crash reports across all sorts of platforms and many of those reports seemed to be where folks had been very ambitious with using VSTs inside it. In one case a guy had about 30 plugins (instruments and fx) running inside Scaler 3 which itself was running as a plugin. Of course, it should cope with that or fail more gracefully but it did seem like tempting fate!
The one thing I never do with Scaler is host VSTs inside it. I just use the built-in instruments for roughing stuff out then route the MIDI to FSP tracks for the "proper" version.
In the early days of Scaler 3 there were loads of crash reports across all sorts of platforms and many of those reports seemed to be where folks had been very ambitious with using VSTs inside it. In one case a guy had about 30 plugins (instruments and fx) running inside Scaler 3 which itself was running as a plugin. Of course, it should cope with that or fail more gracefully but it did seem like tempting fate!