You can accomplish this with unverified Perl. Here's how I created the first "best" radio button in my free format:
[% Begin Unverified Perl
my $exerName = 'MXDF';
my $ffBaseName = 'FFMXDF';
my $qnum = QUESTIONNAME();
$qnum =~ s/$ffBaseName//;
my $thisBestWorst = $ffBaseName.$qnum.'_b';
my $thisMxdSet = $exerName.'_'.$qnum;
RADIOSELECT($thisBestWorst, MAXDIFFDESIGNVALUE($thisMxdSet, 1));
End Unverified %]
To create the second, third, fourth, and so on "best" radio buttons, simply replace the '1' in line 10 with '2', '3', '4', ...
To create the "worst" radio buttons, replace the '_b' with '_w' in line 7.
Once you've got the first free format question set up using this unverified Perl, I believe all copy-and-pasted free formats should have working radio buttons.