Naw, I wouldn't call you a sand bagger. I think you have awesome results but I would grant you a full season in sport with a possible move up after a full year. My old boyfriend was a mad sand bagger in sport and it drove me nuts. Do a full season in sport and get your "legs" together.
I know it's not cycling but my older brother was one rocking motocross racer. He was damn good and won a lot of races really fast. He had to class up and started getting his butt whooped and it sucked all the fun out of it for him. I think he got a bit lucky in his races. Not discounting your skill or his.
In horse shows you leave a novice class after 3 first place ribbons in it. Just because you're doing good in sport doesn't mean you need to leave it. Leave it when the challenge is gone or the rules say you must.
Wish I could have even hung in sport. I never learned to run my own race. I'd lead the beginner/sport class for 5-8 miles and then blow up because I went to hard so good for you for learning to ride your races right. Use next season to hone that skill and ramp up your mileage.
"True, but if you throw your panties into the middle of the peloton, someone's likely to get hurt."