Are 15" wheels worth getting on a Spider?

["Ken Ross" <Kdross@domain.elided>]

My "new" 1990 Spider Graduate currently has the standard 14" wheels and my
mechanic has recommended that I purchase a set of 15" wheels.  He claims
that the handling improvement is drastic and worth the money.  The mechanic
has a set of 15' wheels that he would be willing to sell me for $100 a piece
(i.e. $400 for all 4 wheels).  Since I just bought the car, I think that it
would be best to drive it for awhile and see how the car handles.  I have
only had one chance to really drive the car hard and the car did slid around
a corner more than it should have, but this may just be crappy tires or the
incorrect tire pressure.   Any advice would be greatly regarding tires and
wheels would be appreciated.  I will be using the car as my daily driver and
have no intentions of racing the car.

TIA.

Ken

------------------------------