Aimless Gamer wrote: I wish I could of upgraded from my $300 package to the $500 one. so I bought a few extra digital copies.
Well, here's something you might want to try.
From
these two threads on Facebook, it seems you can get around the $250 upgrade limit by asking Fangamer to combine multiple accounts, regardless of whether they were originally paid through Kickstarter or the Slacker Backer.
In the first link, the user was able to increase his reward to the $300 tier by merging a Kickstarter account and a Slacker Backer account. In the second link, though dealing with a smaller total, it was confirmed that the user retained his Kickstarter-exclusive rewards during the merge.
So basically, what has been proven in practice is that in your case you could make sure your Slacker Backer donations add up to at least $200, and then email Fangamer to merge all of those with your $300 Kickstarter donation. This should enable you to get the $500 tier with Kickstarter-exclusive items from your original KS pledge intact.
Have a read of both threads and email Fangamer to confirm you're able to do this before making the extra donations, but it seems to be a proven workaround.