hello, sorry for delay on answers these days, i'm out some while.
If still you have problems with correct resize in some circumstance, it depend by the iframe code, or the phpBB template or even WP template. Yes this is maybe obvious. In various installs i've try out, with different themes, this not happen.
The reason why the resizer not work properly in some circumstance/page with some theme (and prosilver) i've never go deep in to understand why (because where i've install it on request, normally with premium themes installations, this commonly not happen)
Next 1.7.9 will be focused to improve the iframe about several things and i will try to resolve, or provide an hint, if no fix suggestion about this come out in the while-