I started off with a pair each of LRM 10's and 15's, but I had occasional heat problems due to the ghost heat effect. When I fired all four LRMs, my heat would spike into the 50% range, I had to cool off between salvos.
By dropping the chest racks to a pair of 5's, things are much more manageable. (I toyed with a single LRM10 in the chest, but any heat benefits weren't enough for the weight/space tradeoff to be worth it IMO.) Fewer missiles per salvo, but fewer pauses between salvos, as well.
I can also fit in a bigger engine, which lets me put more heat sinks inside and lowers the heat even more. I also stuck a LPL in the chest so I could run a TAG without giving up as much punch if I end up brawling.
In case it's helpful, here's my build:
B-LRM40-1S
Specific tips: move the AMS ammo to the head. True, it could blow up your cockpit, but if you take a crit there, you're probably dead anyway. In my experience, people generally shoot the head by accident. Getting the ammo out of the chest is one less slot that could blow up and cause you to lose the engine, which people
do shoot at on purpose.
I'd also invest in endo-steel and add more armor to the legs to lessen the risk of an ammo explosion there. I usually max out my arm armor and put about the same amount on my legs. Going lower than that makes me nervous.