I can only fix problems that I can reproduce with the latest versions. Even if a problem does exist in an older version the first resolution is to upgrade to the latest version and see if it still happens. If it does then I will try again to reproduce it and if I were able to reproduce the problem I would fix it and then release a new version with the fix. So any resolution to the problem from my end is going to require upgrading to the latest versions.
The only version of Form Wizard Pro newer than 2.6.6.1 is 2.6.1.2 which is the latest version and requires mojoPortal 2.3.9.9.
I'm not sure what you mean by a slightly newer version unless you mean of mojoPortal but if you are upgrading mojoPortal there is no point to upgrading to any version but the newest, it is the same amount of work to upgrade to mojoPortal 2.3.9.9 as it would be to upgrade to 2.3.9.8