HI,
The Tigertail 4 is a larger model wingspan is 70 inches and fuse is longer as well. Model looks close to the origional but overal 10% or so larger. designed for tuned pipe and all built up balsa and ply. No foam wing and stab. I have plans for both the Tigertail 4 and the origional Southern r/c Kit. Somewhere there is a person that is kitting the fiberglass and foam Tigertail 3 which is in between the origional and the 4. All are great models and fly very well.
Thercav8r