If that's for a carpet of hc you won't need that much. And yes you can have 35 watts over a 5.5g as long as its not right on the surface, try a 6" lift. 18w over a 4g is fine. You can use only excel with these options. People might have different opinions though, that works for me. I have 26 watts over a 5g with excel once a week, 18w over a 2.5g with excel once a week, and 19w over a 1g with excel once a week.