Hmmm...my two cents here:
In general, I believe that the vast majority of police officers in our country are honestly trying to do a good job. I also believe that there are a tiny minority who are NOT trying to be honest at all, and I also believe that there is tiny minority who are simply total sticklers for enforcing whatever laws they're about at any given time.
I also am one that believes in being polite and respectful to officers (part of my upbringing on manners in general). There is darn little, if anything, which can be said to be positive in being less than polite and respectful to an officer during an official interaction.
That said, I'm not about to consent to a search, even knowing I have nothing to hide. Why? KNOWING I have nothing to hide doesn't mean that the officer won't find SOMETHING illegal that I didn't know about. For example, I've had kidney stones and have had narcotic medication prescribed to me. What if a forgotten bottle of that medication was in my car and it was two years past the expiration date? Hmmmm...
I am a SC resident who works in VA a lot. I have family in Manassas, VA and on occasion during visits may, indeed, cross over into Maryland. As a responsible gun owner, who knows how much of a PITA Maryland is about gun laws, it behooves me to become intimately familiar with Maryland's laws as well as the federal laws on interstate transportation of guns, and to make sure I'm in 100% compliance with them.
Also knowing these issues with Maryland, part of setting myself up for success would be to prepare the details beforehand. I can print out the Maryland State Police website information on this matter and have it with me, as well as the Maryland statutes, so I can demonstrate I'm in full compliance with Maryland law. I can print out the federal statutes on the matter so that I can demonstrate I'm in full compliance with federal law. And, because of the convenience of modern technology, I can even take pictures showing everything properly stored in full compliance with all the laws.
This may not stop a search. It may not stop an arrest. But it CAN work as an affirmative defense on my behalf after the fact.
Other things to think about:
- I-95 is a drug corridor. Common sense says that, knowing this, it would be reasonable to assume that the Maryland State Police would be more diligent about stops along this path than they might otherwise be elsewhere with respect to finding reasons to search vehicles. You don't have to like it, but you DO have to understand this.
- Do not knowingly give them a reason to pull you over in the first place. Though everybody knows that with the lengthy motor vehicle codes in place any police officer could find SOMETHING to pull someone over for if they really wanted to, it makes sense not to simply hand them an excuse. Don't speed is probably the biggest. Make sure your vehicle is in good repair. Watch your signaling and be careful not to drift across the lines. Don't drive like an idiot.
- Carry your CCW permit in a fashion which doesn't bring it into view unintentionally when you have to dig out your drivers license and such.
- Think before you open your mouth. Lying to a police officer is NEVER a good idea, but it is not unreasonable to assume, knowing what we know about Maryland and guns, that an officer who has just pulled you over MAY ask you a direct question about you having weapons in your vehicle. Answering the question honestly and saying you do have one in the vehicle does NOT constitute giving consent to search. It may give him probable cause, but that's NOT consent...and if he ASKS for consent to search, then the answer is "no". Giving consent opens up the world to anything he may find. Probable cause narrows this down a LOT. I'm sure a defense attorney would appreciate any such details in your favor.
. Get your documents, vehicle information together & do not fidget around. 
