I'm not sure how the Flash reports work in RSRD. Are you getting a popup message? If so its probably something scripted.
Radio reports in general, work just like SH3.
As to the US TDC, you an work it like a german one. I've never had time to learn the method, but i think its called the "Dick O'kane" method. He doesn't use the Position Keeper. Rockin Robbins has posted a tutorial on it somewhere. Try checking this thread:
http://www.subsim.com/radioroom/showthread.php?t=146795
As to making the game more challenging, has been a driving factor behind ALOT of the things ive done. The stock game sucks. No denything that, and as a student of both the PTO and ATO, i cannot in good concious make the JP ASW as good as the allies. My goal is harder, but just short of what i call, "atlantic hard". It has to be plausible. So what i'll typically do is find some excuse to increase the difficulty.
Take planes for instance. With SD radar, you may as well remove them from the game. What are the chances of being caught on the surface? Then, while putsing around, discovered how to make planes detect submerged objects. Well, thats great, it makes them a threat again, but how am i going to put that in the game and be in context ? Ah Hah! pacific waters were clearer, there's my way to bring this in!
Or another one of my favorites. The type C and D escorts. They had a crapload of throwers, i decided to
leave a couple extra throwers on. In theme, its historically accurate, in specifics, i took some minor artistic license, by a fudge factor of 2 y guns. The excuse i used here is, "nobody will notice a couple extra Y guns during play, they'll be too busy crapping their pants". It wasn't specifics i was looking for anyway, it was the end result while still being plausible to the theater.
One thing that throws a monkey wrench is thermal layers. I love them as a player, but as a modder i hate 'em. It's very hard to adjust sensors without lowering the effectiveness of the layer. Something i tried to avoid. However in version 2.0, the effectiveness of thermoclines is indeed reduced for AI passive. Doing so has allowed me to obtain a more sane setting both above and below the layer.