My humble opinion from MANY a mosquito filled night in Northern Minnesota / Isle Royale / Boundary Waters where the mosquito RULES much of the year- Mosquitos will find a way into your shelter if there is any spaces at all- Anything.
Even if you can reduce the number of skeeters by 95%, that's not the point: The remaining 5% of normal is more than enough to keep you awake and swatting. Heck, I've been kept awake by ONE of them buzzing me.
I've found the only truly effective option is a 'real' tent-type shelter with full enclosure. Other, lighter methods can be effective, though not as much and are often a pain to set up.
The best lightweight option I've used is the combination of a half-length home made bug bivy (think something like a giant head-net) with a couple guy-outs and DEET. I've tried dozens of other, less harsh repellents, and DEET is the one that works, plain and simple. I've been able to somewhat reduce my exposure to it by carrying a designated DEET rag which I spray and hang on a little cord above my head as I sleep.
Hope some of this helps you out.