There is a hole about 2 inches in diameter on the heatshield on my svt exhaust. Would using one of those exhaust repair kits be a good idea? Would doing so negate heat shield-esque properties in that area and thus make it unsafe?

Those $6 exhaust repair kits are fine. My heatshield was making a rattling sound and flexipipe braid was coming out. I took it to the local indy and he said, they usually just pull it off. So I put a strap/clamp on the heat shield and use the "gauze" for the flexi-pipe to hold the braid in. The repair kit (Mr. Exhaust, I think) comes with "gauze", strap/clamp, screws and bolts. You need metal shears (also sold at Advance or Autozone) to cut the correct length for the strap/clamp.

Edit. .... or you could pay $520 for a new main catalytic converter with a brand new heat shield and $100 to install it.