We had the entire Simons kit installed on our 4038 a couple of years ago. The kit was their "extra tall" or whatever they call it, meaning it came with the taller wheels. Also included the reversing fan.

The modified 4038 worked just fine. Gave plenty of height. There are a couple of extras we did that we did and some things you'll have to do to make it work even better.

When working in the tall mode for corn fungicide,  you'll have to remove the side-fill plumbing. You'll want to use the front fill only. Again, this is only during corn fungicide spraying. We also modified the bracket on the front fill to move the fill coupling up higher to avoid contacting corn. We cut up some old 4038 plastic sprayer fenders to make shields inside and above the wheel motors to keep corn from rubbing hydraulic hoses. We had a clear plastic "nose guard" made (Plastic company in Gibson City IL) to help keep the radiator screen clean. Between the automatic reversing fan and the nose piece, overheating was never a problem. In fact the sprayer ran at same water temp as in non-tall crop configuration. I would suggest full wheel covers. Simon now has their own available. The idea is to prevent the torque hubs from hitting corn ears. 

A few weeks back someone posted not being able to get the rear of the machine to full height while fully loaded. That could be a problem, but we normally solved it by always folding booms for transport for filling. Once the air bags fully extend, they tend to stay that way. If you're moving to a different field, you don't want to move down the road in full extension. However, just before entering the field raise the machine fully & you'll be ready to spray when you get into the corn.

You'll want to spend a little extra time tying up hydraulic hoses to keep them from rubbing on corn.

If you want to use floater tires for spring preplant ops, you'll need different wheels/tires for that also since the tubes stick further down in the wheels when not extended. You'll have 2 air line switches in the cab to raise the machine to "mid height", or to "full height".

It's a good kit. It did not cause any problems with the 4038 in normal ops either. You didn't know it was even there.