I am a bit late to this discussion, but just wanted to add a few things:
I can recommend this document on the theory of fractional betting by Ed Thorpe. The whole thing is worth reading, but pages 19 and 20 are of particular relevance to this discussion. In them, Thorpe walks through finding the optimal bankroll fraction to risk in the following situations:
To find them we solve the following maximization problem:
max g(f) = E[log(X_{n})]
That is we are trying to find
f_{1} , f_{2} that satisfy:
d g(f_{1},f_{2}) / f_{1} = 0
d g(f_{1},f_{2}) / f_{2} = 0
(these should be partial derivatives, but I cannot figure out how to typeset them, but you get the picture.)
You can find the answers in the linked document if you are interest, it is just a bit cumbersome to type, but the basic intuition is that:
 for independent, simultaneous bets, you bet a little less than Kelly, but not much less. If you are employing a fractional Kelly scheme (betting something like halfKelly) you do not need to really adjust anything at all.
 for dependent outcomes you bet anywhere from halfKelly to half your bankroll(!!) depending on if they are positively or negatively correlated (as has been pointed out earlier in this discussion)
Does this generalize to more than two bets? That is, to calculate the optimal bet size, do we just need to pairwise correlation of each of the bets (or if you prefer, the covariance matrix)? Though it is perhaps not obvious, the answer is no.
To solve the optimization problem stated above, you need to be able to calculate the expectation at each feasible point, which requires the entire joint probability distribution for all of the bets under consideration, which is reserved for the doublesecrettripleplatinum skratchtoolsmembers.
With that lengthy (and basically pointless) preamble in mind, I think that when it comes to golf betting there are two examples that are particularly instructive, and may provide rulesthumbthat cover a large portion of the instances where this really matters. It is often the case that DG will have a disagreement with a sportsbook over a particular players skill on a given week. These will often present as:
 +EV towin, top five, and top ten bets, top twenty bets
 +EV matchups and 3balls
These are qualitatively a bit different from each other, in that “the event that Cameron Young wins the US Open” is a strict subset of “the event Cameron Young finishes in the top 5 at the US Open” (and so on), where “Cameron Young beats Kevin Kisner in a matchup” is correlated with "Cameron Young beats Jordan Spieth and Max Homa " in a three ball, but it is not a subset of it.
Top 5s and Top 10s, etc
Consider for a moment a situation where there is a +EV top 5 bet and +EV top 20 bet on the same player. These seem pretty correlated, so what should we do bet half the usual amount on each? Here it becomes important to consider at a more granular level the source of your disagreement with the sportsbook. In particular it is useful to observe that when you place a bet on someone to finish in the top 20, you can think about it as placing two separate bets
 One bet on the player to finish in the top 5 (at whatever odds offered by the book)
 One bet on the player to finish in position 620, with odds implied by Implied Probability of top 20  Implied Probability of top 5
Consider the following example, which is from some random tournament from November of last year. DG had Oliver Bekker top 5 and top 20 as +EV. The leftmost column is a 1k bet on Bekker to finish top 20, and the next two columns break it down into the equivalent bets implicitly placed simultaneously on a top 5 and a 620.

Top 20 
Top 5 
Finish 620 
Book Probability 
0.33 
0.10 
0.23 
DG Probability 
0.42 
0.12 
0.30 




Betsize 
$1000 
$300 
$700 
Payout 
$3000 
$3000 
$3000 
The crucial thing here is that a bet on a top 5 and a bet on 620 have negative correlation, so you do not have to size down your bet from your typical fraction kelly scheme. Something you might do in this case then would be to:
 Figure out how much you want down on the top 620 bet. If the answer is zero, bet zero on the top 20 bet.
 Place the top 20 bet that corresponds to this amount
 Figure out how much you want down on the top 5 bet. Since you have already bet on a top 5 (implicitly) only bet the remaining amount to get you to the desired fraction of your bankroll.
Matchups and 3 Balls
Here I will say that if you are not interested in simulating the outcomes and solving the optimization problem stated above, and are looking for a rule of thumb I would say treat these events as highly correlated and do the following:
 Pick the bet with the bigger edge.
 Calculate the fraction of your bankroll you would wager on just this bet– call this f1
 Go to the smaller edge, and find f2
 Take max(f1,f2). This will be the total amount you risk. Suppose without loss of generality it is f1.
Find new_f1, new_f2 that satisfy:
new_f1 + new_f2 = f1
new_f2 = f2/f1 * new_f1
And watch the money pile up baby!