I have a 05 Levin that I changed the stock 21mm hollow rear bar for a Whiteline 22mm solid rear bar and it made quite a difference to how the car handled, still on stock springs and shocks.
The handling is much more neutral and flatter.
The bar was quite easy to replace, just those 2 bolts although the Whiteline bar was about 1mm short as I just couldn't get the bolts back in, so had to heat the bar up (sun and boiling water) so that I could get the bolts through and it was easy after that.
Cheers Col.