Congratulations on your purchase.
I have had a 4-star 40 and I consider it one of the best aircraft I have owned.
As for modifications, there aren't many.
I strengthened the rear fuselage by gluing in som strands of carbon fibre behind the rear wing mount because I had heard that this was a weak area. I don't now if this action was necessary.
Also, I used a DuBro (or was it Sullivan?) tail wheel bracket, instead fixing the tailwheel directly to the rudder.
One thing you might consider is to shorten the wingspan by one bay each side, by mounting the ribs proportionally closer to each other. Apart from reducing the wing span somewhat, the plane becomes a little bit more lively in the roll and the landings become easier (with the big wing it will glide forever).
Also, when you get some experience with the flying characteristics, consider moving the C.G. around a little bit.
With some tweaking you should be able to get the aircraft to fly straight and level both inverted and right way up without any trim change. This is the only aircraft I have had that could do this.
The only flying characteristic I didn't like was the rather strong nose-down pitching tendency with rudder application. It seems to be a characteristic of all 4-stars and if you are aware of it will not cause any problems.

/Red B.
Sweden