🚀 go-pugleaf

I was wondering whether anybody could help me with the following
problem.  I am writing up a PhD thesis which is getting fairly large,
and as a result I am running out of parameter space.  The problem arose
when I tried to convert my subscripts to non-italicized letters.  That is
rather than use $t_{start}$ I used $t_{\mbox{\scriptsize start}}$. 

Can any body give me a fix.  I see two possible solutions;  one increase
the parameter space, however, since the problem seams to occur early in
the run this may not be practical; or maybe there is another way of
making non-italic subscripts that doesn't chew up the parameter space.

The error also seems to occur when the above appears in a figure
caption.  Could that be a problem?  I'm not exactly sure but it looks
like the problem occurs when the lof file is written to. I performed the 
function by using a \newcommand ie:
\newcommand{\subs}[1]{{\mbox{\scriptsize #1}}}
Does this need to be protected in some way?  

Any replies would be appreciated by email.  Since I am witting up I find
I spend less time reading news. (email strick@mullian.ee.mu.oz.au)

Cheers Larry