I say - stick with it. Why? Because you wont be getting a better start anyway. Your expectations seem a bit off - occasional oversleep is more like the norm during transition, not the exception. After all youre probably getting incredibly sleep deprived, because the naps you take consciously are not refreshing you. So your body forces you to get some real rest and you cant do anything about it.
What you can do is program yourself well, so that those unwanted naps take as little as possible. I told myself that If I could go 40hours without sleep, I should be able to stay awake for 3 hours after a 30min nap and so when I took the occasional unintended nap (or forgotten alarm) Id wake up in 30mins and keep awake.
The other solution to the problem is to learn to sleep right, so that your subconsious doesnt need to override your decisions anymore.
Im gonna share what I found out for myself from my 2 attemps (first was ok, but the second is awesome now.
In my opinion, the problem with adapting to polyphasic sleep isnt so much in discipline or persistance or having the willpower to stay out of bed until you finally adapt.. Its in getting the maximum rest from the naps youre getting - learn to fully relax your body (might try sleeping on your back) and mind (eliminate all chatter) and tell yourself (your subconscious will carry it out) how long you want to sleep and how you want to feel after that.
Ah - breath deep and stretch after you wake up. Make it a solid habit - its incredibly important for your energy level, after 30secs of breathing exercise I find that the brain fog disappears entirely.
Might add also a big smile and a confirmation like "Im fully awake and in control".
Also find something interesting and vitalizing to do right after you wake up. Certainly not reading.. Online poker is perfect (or any fast-paced computer game), but your eyes might get sore after a while. Tune down the brightness and stuff, relax your eyes and instead listen to some music.
And if nothing else helps you stay awake watching porn does..
I myself couldnt quite adapt to full polyphasic last year, i found it really inflexible. I guess that if you really master it - fall asleep and wake up at will - it will be great, but it was tough for me. Core sleep + several naps on the other hand is so much easier and more flexible that I think everyone should try it. Im sure I can transition to polyphasic sleep now easier than ever too.
I think the most important thing when trying to master your own sleep schedule is the self-programming youre doing to yourself. You MUST remove all doubt and negative outcomes from your mind and replace them with a picture of what you want to happen. And keep looking at that picture, no matter what happens with your schedule. Youll screw up once or twice, but eventually this picture will guide your subconscious into making the changes.
If you imagine negative outcomes in your mind you will reinforce your subconscious into carrying them out. The whole secret to successful adapting lies in the right self-programing imo.
I had scripted myself quite heavily last time and was very pleasantly surprised - Id fall asleep accidentally and wake up in 30mins or forget to set up an alarm and wake up almost at the right time anyway. And I wouldnt blame myself for falling asleep, but rather feel happy that my subc would take care that I do get some rest, but still allow me to progress toward my goal.
Im now sure that everyone can learn to control his sleep - its just that people never try to.
Before trying out polyphasic sleep I had a really hard time falling asleep and waking up. And falling asleep and waking up 5 times a day certainly helps your learning experience.

So learn to sleep right. Its a skill. It takes practice.
Question--> How do you people have full lucid dream naps? Can you describe the process between lying down and falling asleep? I try to eliminate thoughts and instead focus on pictures, sounds etc, while remaining conscious, but I usually either lose consciousness or just as I start falling into the dream I get somewhat excited and "wake up".