Hi Platt,
Yes - it is absolutely possible to have Tekken 3 on 6.60 pro, because I also had been struggling with this recently but now have it running.
I have updated to PRO-C but was previously on B10, as you are currently.
I used ISOBUSTER v3.0 to extract the raw dump from my CD, to a .ISO file.
Having tried other options such as PSX2PSP without success, I then used the brilliant "Simple Popstation GUI v3.00 Beta" to convert to, and transfer, the EBOOT. Using a compression level of 9 gets this down from 658 Meg to 479 Meg, btw. This version of the GUI does recommend you not use .ISOs and encourages other options, but I proceeded with the .ISO I had ripped.
In terms of the Popsloader, I installed Popsdeco's "Popsloader V4E" which is the modded version of the official PRO team's Popsloader v3, released last August.
Versions 3.03 and 3.04 (as selected from the Popsloader menu, with the R button held down while the game boots) will run the game, but with the display too far down the PSP's screen.
Versions 3.10 through to 3.51 all run fine with the screen centred but these early versions have the disadvantage of not having the "Custom" screen mode option in Settings (when pressing HOME in-game).
Versions 3.52 through to 5.03 run and display okay but the anti-piracy and "Namco presents" screens both have a strange line of brown pixels towards the bottom-right corner (including the recommended 3.71 Pops).
However, versions 5.50 through to 6.60 all seem to run perfectly with no quirks or glitches, although the very useful feature to custom-resize the screen does not come into effect until version 6.00
In summary... persevere because this is possible! It could be the quality of your CD image, but given that I had varying success using the same image but with different conversion products, personally I would say it is as likely - if not more - to be at that stage where your issue is. The product I have mentioned was the one I found the best, not only for the obvious reason it worked for me where others failed. If you were to follow the approach as I have only today you will hopefully have the same success.
I hope this is of help to you and anybody else in the future who may have trouble getting this game to run on PRO CFW.
Good luck