The Ultra Sport 60 is fantastic plane..I built my wing over the plans and it was very easy but I have a fair amount of experience..The US does come with a wing jig to help you keep the wing straight...I used E Flight electric retracts and am very happy with them..They are very easy to install and work great although I found the wire legs a bit soft and easy to bend..I made new ones out of music wire and they are standing up much better. I haven't built a US 40 so I can't honestly compare them but it has been my experience the bigger is better..Easier to see,easier to fly, penetrate the wind better etc etc..I am using an OS 75 AX on my Ultra Sport and it is a great match..I would not use a four stroke on an US . The hinge slotter is super handy. It is well worth having...It makes installing hinges so much easier...