we are new to tandems started out with t-100 trek this year upgraded to t-200 after sister wanted old one now we are enjoying the tandem ride enough to go up again but our lbs only carries a low end the 200 is fine except we can not stop on long hills also stoker complains about rough ride ,without breaking the bank what do we need to look for we ride roads and rails to trails what exactly are the differences we have done a lot of looking online but are getting more confused for instance we now have a 21 spd but never use lower gears any help appreciated