Rehd, at that leght you could easily get a block of foam and carve your own half shape then slice it to find your forms, but if you want to avoid the mess...
As said its best to not remove forms, just reduce the distance in between them, if you want a canoe that tends to keep the look of the longer sisters just reduce the distances gradually: a little more in the middle than the ends (and will look like this 10ft http://www.islandnet.com/~canoes/prod01.htm ) if you reduce all the distances in between the forms equally youll easily end like this http://www.wooden-canoes.com/canoes/whisper.htm, specially if you start with a long hull.
Since you start from a short canoe already you will have less problems with mantaining the shape.

An outer keel, and you can make it run the whole lenght of the hull, will improve tracking enough to keep a rounded bottom plus since its kids paddling will protect it too, and in that case i would consider adding the sacrificial outer keel after the glassing, it will make glassing easier too.
Keep the tumblehome, eventually you can add a little more so they can paddle without tilting the hull sideways while they try to reach out with the arms.

If you want to reduce a longer design, lets say you start with a 15ft that is simmetric you can try eliminating the middle station, this will leave you with a narrower beam that would be ok on a 10 ft, at that point compare the two stations behind and in front of the eliminated one and if they are the same shape everything you need its checking with a batten that the curve its ok after having reduced your forms spacing. Choose a design that doesnt have much rocker because eliminating the middle station practically will leave you without the straight part of the keel.

Short designs you can easily work with are the Rob Roy and the Wee Lassie and im sure you can find the lines somewhere online for both otherwise these guys can sell you the plans http://www.adkmuseum.org/
And you can check this:
http://www.feathercanoes.com/html/wee%20lassie.html (copy and paste this one: it misses the lassie part)
http://home.hiwaay.net/~sbuc/canoe/wee_lassie_log.htm (and see how he changed thinghs with not many problems)

Then there is the Laughing Loon series of Wee(s) that can give you an inspiration.

some offsets can you can adapt are available in the E-book "Canoe and Boatbuilding for Amateurs" at http://dragonflycanoe.com/stephens/

and give a look at the thread http://www.kayakforum.com/cgi-bin/Building/index.cgi/review/159998 for some other links

Remember that canoes were built without plans and they were working well so dont be too scared to whip up a design, some cardboard for forms and a few battens will let you prepare the templates for your really own boat.

: O.K.. No responses as to what canoe can be altered and built at or under 10',
: so I found a friend that has molds for a 12 1/2'er. Beam 34" and a
: reasonably flat bottomed center section. The semi-flat bottom runs for
: around 3 1/2 to 4'. Sides are approx. 12" with a little tumblehome.

: My questions are: If I remove the center two forms and bring it down to 9
: 1/2' long, keeping the 34" beam, a little of the flat bottom, keeping
: the same basic shape to the stems, will I loose a lot in the tracking
: area. If so, will it help to wrap an outer stem down and continue around a
: foot or two on the bottom, tapering into the bottom.

: The reason for the shorter canoe is that I got enough wood to cut 540 strips
: of poplar, 1/4" x 7/8" x 10'. Also got approx. 20 stips of
: redwood from 8' to 20'. So, I want to build a few short canoes for the
: grandkids and their friends to use up some of this wood, then I can use
: the rest to add some detail to a kayak or three. These will be kids with
: little paddling experience and the better they track from the get-go, the
: better chance they will have to get where they're going.. The semi-flat
: center to help with stability.

: Thanks for any ideas..

: Rehd