YES (and unfortunately....no.)
Yes in the sense that you can MOST DEFINITELY have a good quality attraction within a scair structure, I have done it for an event that was only one night in the past. As with most haunts, your actors will make or break it, but the scair structure is nice because it can still fit full 4x8 wall panels, and the d-rings make running wires and air lines VERY simple.
Unfortunately, they only manufacture it in black, and are rather short regardless of how maze like you make your layout, so I do not see how a circus/clown theme like you mentioned would work at all, the large inflatable black columns probably wouldn't hold paint very well (and I wouldn't recommend painting the poles EVER...you have to break it down and inflate it many times...most paints would probably cause the columns to stick to each other in storage/deflation) or would just flake off...I really wouldn't do it, and what circus/clown haunt makes sense with black columns everywhere?
If you're determined to do the clown theme, I would recommend a trailer haunt for quick and temp set up. One trailer would be about as long as a scair structure, but you could also make the sides fold down to triple the size (I believe shipwreck productions uses that method in a lot of their trailer haunts...they're something you should look into).
Or if you want, start little by doing scair (like you want) but do a cool pitch black haunt and do a bunch of classic (but very effective) pitch black scares, it'd be more cost effective, easier to pull off in a shortened timeframe and would still allow for your guests to feel like they got their money's worth without breaking your bank, plus you'll have a blank slate for next year and can use even fewer actors! (With the pitch black theme, and the black Velcro vinyl wall panels, you can leave the bottom corners open (not velcroed) making it so one actor can consistently jump ahead of the patrons unnoticed, something you couldn't do with any other theme). Just a thought.
Not trying to change your direction or tell you what to do, but a scair structure is just not very carnival/clown friendly....and if you really wanna start small, a different theme would probably save you money, and your guests would be none the wiser.
Plenty to think about, best of luck to you!