Wire Size & fuses for solar install

#10 is too small. I will guess your panels Isc is around 8 amps. 4 of them in parallel is 32 amps coming into the controller. You need at least #8 but larger would be better.
The output of your controller could potentially be well over 40 amps. I'd say #6 is a minimum on the output. Larger would be better given the distance.
Don't forget you need a fuse in series with each of your parallel connected panels. This prevents 3 of them from shorting all their current thru the 4th one if it ever shorts out. The device commonly used for this is called a combiner box. Your panels should list their maximum series fuse on the label.

35' seems like a long run to get to the controller, especially for 10ga

Some great online resources I found when doing my research.

HandyBob's Blog « Making off grid RV electrical systems work

Kelly's RV Solar Blog | All the Electricity we need and then some!

RV Electrical


I probably went overboard but I used 4ga for 15' run, but I didn't want to ever worry about it no matter what I might add later.

Your Morningstar instruction manual will give you the size fuses necessary. 10ga wire appears very light, especially for that length of run. You're looking for NO MORE THAN 2% voltage drop over your wire run. We are using 6ga from an on-roof terminal box to the Morningstar controller and are only running about 16 ft. The same from the controller to the batteries about 2' further along. Look up Handy Bob on Google and be prepared to do a lot of reading, but you'll also be getting a post-grad education in solar installation and care and feeding of your DC system. We have four 140W panels (tilt-able on all primary axes) and a Morningstar Tri Star MPPT60 controller. We've been running it since Jan 2013 and boondock extensively in the southwest and Alaska. Our system is outstanding. Another site with good educational info is Northern Arizona Wind and Sun.