Something

#!/bin/bash
package='thunderbird-2.0.0.9-i586-2vl59.tlz'
mkdir explode
cd explode
explodepkg ../$package
cd ../
size=$(du -bc explode | grep total | sed 's/	total//')

# You won't need any of above code after package as you will already know the size of $PKG
# It's just needed to get this demo going.

installpkg $package > /dev/null 2>&1 &

fifo=/var/log/setup/tmp/fifo1.$!
until [ -e $fifo ]; do
   sleep .001
done

./pv -i 0.1 -s $size $fifo > /dev/null