That is perfectly fine but as previously mentioned, you might get some rubbing. If you have stock rims, you will need at least a 1.25" spacer to avoid the rubbing and at least a 2" lift to avoid hitting your fender (while flexing).
Be very careful when considering putting brackets and having the fiberglass top fully supports any roof rack system; depending on the weight you put on the rack, eventually the fiberglass body will crack and it will cost more to either repair the body and/or replace the roof. Do it right the...