My contention is that bidding changes depending upon the target for which you are aiming. In other words, if you make a game try, partner is within his rights to jump to that game and eat up all that lovely investigational room. Suppose on the hand in question you have deemed a 3D continuation a help suit game try - so you bid 3D and partner with Axxx, x, AQxxx, QJx jumps to 4S. Not much help for slam. Some may solve this by having the jumper cue bid on the way, but this gives away valuable information to the opponents when game only is being investigated.
The thought has occurred to me that there is a simple way to separate these hand types without much if any loss: a forcing self raise.
1D-1S
2S-3S* Game force, slam try.
In this sequence, partner will evaluate his hand in light of slam aspirations rather than game aspirations and the answers do not always come out the same. The give up is little as no one seems to have a really good use of the self raise in this sequence anyway.
I know I evaluate my hand in a different light depending on whether partner is trying to get to a vulnerable imp game or trying for slam. This simple fix should allow an easy separation of ambitions and make slam bidding easier I would think.

Help

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ing) tr. v. - Any bid made by bridge player with which partner disagrees.