Hello; I have built two of these wonderful planes, very enjoyable build, both planes fly great, I used to have a Saito 120 in one but took it out to put in an OS 91 which seemed to make the Ultimate more maneuverable and much lighter. I used an after market landing gear as the original gear didn;'t last too long, which damaged the firewall. I put an aluminum doubler in behind the firewall to double the undercarriage, and have had no problems since. Wonderful flyer, lots of fun.