Unless the max bet is at least a double digit percentage of your bankroll just let it ride the variance is pretty low for bets with double digit plus ROIs
If you have a tiny bankroll a middle/arb weighted equally towards both sides is fine
If you can't bet a max bet of $50 on a 99% to win shot and let it ride though betting might not be for you
http://www.aussportsbetting.com/tool...on-calculator/
Change fractional Kelly to 0.5 (unless you have a high risk tolerance leave it at 1) and that calculator will tell you how much of your BR you can risk on a spot - leave the max risk on the 'correct' side (eg in this case the promo lines being that they're mega +EV) and arb/middle off any extra you can get on the good side, weighted either equally or leaning towards the good side since it's more likely to win than the other side, up to you
FWIW on that Rams spot Kelly suggests 97% of your bankroll, or 48% for half kelly (assuming 99% to win is right on a +38 line, seems about right but not gonna go determine what the true price is for an NFL line +38 vs market pk) so unless your BR is less than like 120 dollars you're fine to shove the 50 bucks on it even with a low risk tolerance