getting ready to brew my second batch

Having just finished construction of my $0.00$ Son of Fermentation Chiller ( though in my case Redheaded Step-Child of Fermentation Chiller is probably a more fitting title), Im getting ready to brew my second batch of beer. It's a fat tire clone using LME + specialty grain. Per my reading on here I plan on ditching the instructions that came in the kit and splitting the boil into two batches instead of adding water to the 2.5gal of wort to bring it up to 5 total. Will do a late extract addition too. Question is Do I need to worry about DMS? I think I've read before that extract brewers don't need to leave the lid off but would like some input from the homebewgods. This dinky burner(BBQ grill) just won't get up to what i think of as a hard boil with 3gallons sitting on it and no lid.

 

I've heard it said (on this forum) that DMS is a non-issue for extract brewers, too, but don't recall seeing any data to back it up, nor do I fully understand the chemical reaction that results in the formation of DMS.

All I know is that it is formed in the boil and evaporates. Malt extracts (at least the *liquid* form) are 'boiled', so I can see why the DMS MIGHT be removed already. But, then again.... they 'boil' the LME during manufacturing a vacuum and at much lower temperatures than the boil you would get in your kettle, so.....