An old time repairman just showed me an unexpected positive feature of horizontal drop outs that I was unaware of. I had been trying to get some alpine gearing in a Colnago with horizontal drop outs that I bought recently. I came up with a NIB Sachs 12-30 freewheel, but doubted I could use it with my Super Record Derailleur. This guy moved the rear wheel back to the rear, added two links to my chain and Voila...everything seems to work fine. A little noisy if one goes big chainwheel to biggest gear, but I avoid this situation, anyway. This is probably old news to you pros out there, but I sure was impressed!
Tom Sanders
Lansing, Mi