OK here goes...I recommend these settings for trick jumping only as they will introduce LAG if you try them online over a dialup.
set com_maxfps variable from the console to something like 150 or 200, this will introduce local lag and the engine will try to compensate for interpolation by making you jump farther. However while trick jumping may be fun I highly recommend you do a
\reset com_maxfps
before joining any servers.
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Commander Keen