SI3 plans and kits are for sale at www.rcairboats.net You can do it either way. Plans are around $35 and the .20 series kits start at around $80. Haven't checked pricing lately so those figures are approximate. Chris (the designer of the SI3) sells a flat bottom kit/plans as well as other stuff. Check out his site (there's a forum too). Lots of builds with pics in the forum. Chris is a super nice guy to deal with too.