At a 20' length, any speaker cable is going to start to play with what your hearing to a greater extent. Given the superior electrical characteristics of the Goertz geometry, this cable will be less of a detriment than other cables at that length.
Having said that, that long of a cable may present somewhat of a task for some amps due to the high capacitance. I sure hope that you're using a Zobel network with them. Cutting that length in half but then using twice as many runs ends up producing the same appr amount of total capacitance. Where it will differ electrically is that series resistance will be cut in half, which may / may not be beneficial in your specific system combo. Given that these cables are already quite low in series resistance to begin with, the differences may be negigible.
As you probably know, i'm a big fan of these cables for many reasons as i've explained many times over in great depth. If you already liked what you had, it will only get better by going to a more reasonable length. I would expect an increase in midrange liquidity and focus with slightly cleaner highs and improved bass definition and impact. I would still recommend using the Zobel's with the shorter length, as they don't hurt anything and may actually help sonically.
As a side note, i would not go too short with these or any other cables. Should you ever want to sell them at a later date, they may be harder to move. I don't know what lengths you need, but from what you stated, it sounded like you had enough to make three sets of cables from your 20' runs. If you can get by with it, i would say to stick with 7.5' - 8' pairs for your own use. This will leave you with either a 4' or 5' pair to sell. Four footers work reasonably well with monoblocks driving stand mounted speakers and five footers work reasonably well with speakers that are mounted relatively close together with the amp centrally located. This would leave you with enough cable to move your speakers about ( if need be ) and leave you with a more marketable product in the future.
With all of that in mind, i would recommend using Goertz silver spades if you have them re-terminated. I hate their banana plugs, Rhodium spades and pin connectors. How they ended up with such nice silver spades compared to the rest of their connectors is beyond me. Sean