It was constructive critism regarding safety. If your so knowledgable you would have known that and not asked the question in the first place and thrown out that age old "do it right the first time" phrase. The 12 volt unit your refering to will not put out nearly the psi that a belt driven OBA unit will, plus it has safe guards built in to regulate the line pressure. If you were talking strictly about bolting in a compressor and not actually taking the time to build a engine driven unit, my appologies, I must have miss understood you end goal.
Honestly If you prefer to carry all of that equipment in the back of your jeep, 12 volt grinder, cut off wheel, drill or what ever you carry none of which requires a compress air source to operate, then why ask about OBA?
Congrats on all the tools you use in the field, I am sure they provide you with much satisfaction, and at the end of the day prove that you have done a good days work.
Lastly since you feel like mentioning it..
Of course you won't find trails listed on the internet in Boston. It's a F-n City, do you sincerely think that people in LA, Chicago, or Houston actually wheel in those cities?
Fact is 99% of the land we recreate on is private land, land that myself, as well as the cooperative work of many individuals work very hard to secure, agree on leasing agreements for, perform land/trail cuts and maintanences. Because it is private, we do not advertise it there for we keep intersurfing dweebs off the land destroying it.
Fact, Over the last 4 years Massachusetts has lost almost a 1000 acres of public land that the 4wd community had recreated on. currently the closest trail to Boston is a scant 2 hour drive. We all can live in Puget Sound.
If you need a forum to research land use in New England here is a couple
Welcome to NEOW.org - the Internet Home of the Northeast Online Wheelers
Northeast Association of 4WD Clubs
Good luck with your search on the components you would like to use.