You're not reducing the odds...they remain constant. This challenge is focused on the five white numbers. The odds of randomly selecting 5 numbers correctly out of 53 are 1:2,869,685. That will never change.
10 number choices is the arbitrary number we have agreed on. It could've been 6,13,18,35,48...or any other number between 5 and 53 inclusive. How tough is it to match all 5 numbers out of the 10 you've selected? Odds are 1:11,387.63888. How do you figure that out? The odds of matching each ball. The first number drawn, you have a 10/53 chance of getting it correct. The second ball, you have a 9/52 chance (only 9 of your numbers remaining, and only 52 balls in the machine). Third ball you have a 8/51 chance, fourth: 7/50, fifth: 6/49.
(10*9*8*7*6)/(53*52*51*50*49) is the probability of that occurrence on any given selection: 0.000087814516227. Take the inverse to get the odds: 1:11,387.63888. In other words, if we had five predictors every PB drawing, we would match 5 of 5 in 1 out of every 2,277.5 Powerball drawings...once every 21 years, 10 months. So, if someone does that soon, it's probably proof that they're onto something beyond random chance.
I think you should design a prediction system around whatever number of selections appeals to you. There is nothing magical about 10 numbers....and if you were lucky enough to get all 5 drawn within your 10, your chances of winning the jackpot on a line from those 10 numbers are 1:10,584.