Class advancement advice

I'd caution against it, until you're forced to advance or absolutely destroying the C competition. Its a big jump in speed and a learning curve for sure. Getting C podiums amongst a gate of 7-14 is likely going to have you in the back of B and frustrated. If you haven't placed first yet, chase that goal. Reach it, then expect to accomplish it. Then move up. Yes, riding with faster riders will make you faster but master and beat the pace of the top C guys first. Moving up too soon can result in frustration with results, which can take the fun out of it and make some burn out. You usually can't go back to C from B. Enjoy beating C for a while, while you can.

Start out C again this season and see how it goes. How old are you? I would wait a bit, you can always move up anytime on any race day. It's doesn't have to be all planned out.

Not sure what association you are racing with but you might talk with the sponsor or a competition member and see what they think about you moving up..

Advance your way through the points system in place! Focus on winning races, one race at a time, then maybe a series or two. Don't be in such a hurry to advance yourself, because if you are in an area that allows for sandbagging in the first place, and you can't beat them, what are you going to do when you jump to the next class? Obviously the guys sandbagging are doing it because they can't win in the "B" class either! Besides, if you ever travel to another area, that has a bigger venue, you will be at a disadvantage against riders that have earned their way to that class, and have more experience than you by doing so the right way. You may feel comfortable riding with faster riders, but I would suggest practicing with them instead, and winning your way up the ranks.

I was forced out of the C/Novice class and into the B/intermediate class when I was 15 because of a ridiculous rule and it was the best thing that ever happened to me in regards to motocross. It instantly brought out the potential in my ability. It was a full gate in a regional race and I ran inside the top 10 for several laps before fading back to mid pack when my arms turned to melons.

After that race I gained more confidence in myself than ever before on a bike and I became a better and faster rider in the years that followed. It was also much more gratifying to me being in the better/faster class and I felt safer during the race knowing every guy was doing all the jumps.

I'd recommend moving up.

I was a good starter in the C class and was a threat to win on any given weekend. When I finally did put one together, it was pretty much like I "decided" to win and I felt like it was about time to move up. I was prepared to not win for a while, and I was cool with it, like it sounds you are. I figured I'd get good starts and then get blown away by the intermediates.
What actually happened is that I got ruined on the starts but was able to hang onto the pack for a while. It helped me get faster and gave me a "carrot on the end of a stick" mentality. My riding improved dramatically in one season and I became a contender pretty quickly.
My suggestion is for you to stick it out in C until you feel like you can grab a win at any time. Then accept the greater challenge of the B class. You don't have to wait until someone advances you.

Jump into a b class session when you practice, thee first few times will be a major shock but you really get to see the correct way of doing things. Just mentally prepare yourself that you wont be the big dog on the track for a while, but like anything with practice comes perfection. Than you can gauge whether you feel prepared enough to jump into a B class race.

Sign up to race C but go out for practice with B guys. On open track days practice with B guys. Once you can keep pace with the consistent guys in your B class jump up and race with them. Confidence is good but you can get caught up riding over your head just trying to stay with them when it comes time to race.