Tantal kits are fairly cheap if you want the correct gas block, front sight, and brake, and you can always sell the extra parts. I think you might even be able to use the RSB as well.. As long as you have access to someone with a lathe to turn the AEG barrel down it shouldn't be difficult. The hardest part will be adapting the tantal safety to an AEG I think. I've thought of ways to do it but none of them involve lowering the safety lever axis so it wouldn't be true tantal. None of them are that good, either..
Also, Dan, a plum tantal has been a dream of mine for a few years. Nothing beats