[CanuckJim]

Balty,

While the cracks may seem unsightly, from what I can see of the photographs, they aren't structural. What I'd do is give it the necessary cure time, then begin a series of SMALL fires to see if the cracks get any bigger and/or smoke appears through them. If smoke leaks, you will have to seal the dome again. It's unlikely that big chunks of your material will break off.

Try to do your coat in one go, fairly wet for a good bond. Depending on the material already there, you might have to wet what's already dry before trowelling on. You want a good, strong bond. Just a question, but if this is a consideration of added mass, why not build a form and pour into it? That way, all you'd have to trowel out is the top.

Jim