I am not a professional on the subject, so if any one out there in internet-land has experience similar to Mike1992's and rx7bandit's please post up. It sounds like Mike could use one, as I assume the "rubbery" feeling he discribes is the onset of a third gear problem. As for rx7bandit, I would say this extender may be a bandaid, but you should get the real wound fixed. You may have synchro damage. You may need a transmission fluid change, which is easy as heck BTW. It seems that when transmission problems wear they cause other problems as a result. I recommend some internals attention.
20G Stage 3 on E85: New data:384 hp 411 tq
"Maybe I should just stick to bolt-ons." -Hitler
I don't really want to wrench anymore. I'd rather detail.