Glad to see your concerned about your snake becoming over weight. It seems like some owners either don't know the snake is fat, they don't care, or they think that it makes it a "bigger snake" which is "cooler" than those skinny snakes!
In short the answer is yes. There should be a bit of a lump when the food item settles. Try feeding the corn a prey item between 1 and 1.5 times its girth at its largest diameter.
For extra guidance, this list may help, its known as the Munson Feeding Plan. Its a guide however and your snakes requirements may be somewhat different than this list, although it has proved very helpful to me!
-single pinks (2-3g) Every 4-5 days. (Snake=4-15g)
-Double pinks(3gx2) Every 4-5 Days. (Snake=16-23g)
-Small fuzzies(5-7g) Every 5-6 days. (Snake=24-30g)
-Regular fuzzies (7-9g) Every 5-6 days (Snake=30-50g)
-Hoppers(9-12g) Every 5-6 days (Snake=51-90g)
-Weaned(14-20g) Every 7 days (Snake=91-170g)
-Adult(24-30g) Every 7-x days (Snake=170g+)
-Jumbo Adults (40-50g) Every 7-x days (Snake=400g+)