I'd like to convert my Trek 4900 into an internal gear bike as it is my commuter now andI am sold on the merits of internal gears. My main question is will my semi vertical dropouts work with a Shimano nexus hub or do I absolutely need horizontal dropouts? I don't want to use a chain tensioner or derailluer. Also, can I avoid the roller brake and use the pull-brakes that are on my bike now. Any other advise is appreciated. Thanks guys. ws