As far as the 12" rule... has been a rule for quite some time and has nothing to do with the "old days" With 2.4 it is much less an issue.. FM / PCM it is worth listening to the people who design the products and following their guidelines. Sometimes it's not always possible to follow the 12 in rule.. but it is good to follow it if possible.
As far as the 6 volt thing on ignition, #1 There is no benefit to using 6v. #2 TKG ie: Terry from CH has stated many times on here in the last couple of months that in his testing at 6v components start to heat up and will ultimately shorten the life of your ignition. By How much? who knows.. but they are still recommending 4.8 packs unless you have the modified 7.4 ignition from them. Of course there are some brands out there that will handle that stock, 3W is one of them.
In short, never assume.. ask people in the know... some of them have been mentioned already, however there are countless threads on here dealing with gas engines.. there isn't muchyou wont find if you play with the search fucntion for a bit. Sometimes it's not the most accurate but a couple trials and you can find almost anything you want. Most times someone has had the same problem in the past and found the solution already for you.
on a side note what is YMMV?