A keel is provided having a spring portion and a connecting portion. The spring portion can have a channel that is compressible during compression of the keel. A variably adjustable compression member can be provided. The connecting portion is rigidly connected to a rigid center support. A heel is also provided having a spring portion and a connecting portion. The spring portion can have a top open channel formed therein. The channel is compressible during compression of the heel. A variably adjustable compression member can be placed within the channel. Alternatively, heel and keel springs located at least partially external of the heel and keel can be provided. The heel spring can act against either the keel or the center support, and the keel spring can act against either the heel or the center support.
