Not sure if that it's a good idea to put the boiler right below the balloon...all that hot smoke, sparks and ash might not do the fabric a great deal of good.
While I almost chided you with 'oh, sure, bring reality into this', in truth, I was rather embarrassed I'd not made the comment first. Will still fly, but I'll blush a little at it.
Me, I was going to complain about how some of the layering worked...
Doug