The custom URL length should have either no max length or one much higher, particularly for using tokens.
For example, one of my more lengthy tokens ends up as [submission:values:personal:occupants_other:occupants_other_1:occupants_other_1_age:nolabel]. The actual value of the token is a two-digit integer, but I cannot use more than two of these tokens in my custom URL.
Another example, I use conditionals to "show" a hidden value for each option of a select field which has a couple dozen options. I want to post the "shown" hidden value for a selection on a PHP "thank you" page, so the URL will have a query string like "q=[submission:values:hidden1:nolabel][submission:values:hidden2:nolabel][submission:values:hidden3:nolabel]..." I have to string together all the hidden values to post the single hidden value that was "shown."