Scott,
Definitly be careful with the smoke idea on a smaller gasser....a little extra weight isn't worth the price in performance on this size..IMHO...

I wouldn't run the extra weight of smoke on anything less than a 40cc gasser.
I have one on my Ryobi 31cc and while under my own recommended size (I'm flying a 24 chord x96 span foamie at 18lbs, 14 oz sq ft loading with it)...so, I can give a little bit on the weight...

The Extra looks awesome...I'm building the GSP Katana 1.40 right now with RCS 1.40 gasser (swings a Bambula 16x8 at over 9000).
Hoping to keep it under 10 lbs (but will be happy with 11 if it happens).
http://www.crazyherb.com/Katana/katana.htm

Even though the RCS is only 23cc it packs a pretty good punch for it's size and is only 3 lbs RTF...

Don't ruin your experience with the Extra and a weedie conversion.....they just don't have the "balls"...this plan DESERVES better...hehhe

Now...a 33cc homelite.....maybe.....but the 45cc is only like 2 oz more and 25 lbs thrust....
This size plane is a killer.....too small for gas really...but too big to feed glow fuel....

Look for a really LIGHT and powerfull 30-35cc....maybe RCShowcase's ROTO 35??

Watch that wing loading....and choose carefully.....best of luck....

Fly hard....land soft...

CrazyHerb