Is the clone restricted for RPM? (either by limiter, valve float, or BANG! if run too tight) What RPM were you seeing?
The WF is limited @ 7100. Some tracks are so tight inside that staying off the limiter on straights leaves you with a chattering clutch and/or no power in the small radius corners. BeaverRun/PittRace is like that for me. On the advice of a local guru, I geared for limiter hit near the S/F line on the front straight, and it was much better inside, lap times lower. Our clutch has the orange springs, because for some of its use we needed the hole shot. If it were to be only used at a track, I might put in some lower rpm springs so that it would stay engaged.
The gear I had on for that track was 15/60, same ratio as you were using on the clone. If you have never been to Pitt: It has a 500′ main straight. But, I was running the last corner, and the esses preceeding it, flat out, and that adds another 650′, with some scrub to slow down acceleration. So, at around 950′ WOT until the limiter hit.
If the clone tops out at 6K rpm, the same top speed in the WF would mean running an 80 gear. Of course you want to go faster, with more power… maybe a good place to start is 68-72?
Disclaimer: I have never raced W2W in the WF, only track days with friends. Still, in 3 separate sessions and with two drivers taking turns, our WF has 300+ laps at Pitt. A couple of hundred laps at Pelee in Ontario too.