William David Bodell:
The clarification of the 'two' paths - insight & concentration - in my practice is helpful but the question of concentration first then insight practice OR insight practice (with the concentration naturally improving) does give me a source for vacillation. I wonder if the doubt about which approach to commit to is limiting my progress. I am due to go on a Goenka retreat in three weeks and hope for some clarity in goal / focus but ...
if it's an issue at all, the answer is probably just do insight practice, as those who benefit most from trying to build concentration first are less likely to struggle or have doubt about this matter in the first place, and those who frequently have doubts and questions are more like to be oriented toward insight, as i surmise that you are. i also gather, from one of your earlier posts, that you have already been over the a&p, which means, according to the visuddhimagga, that you understand what is path and what is not-path, and from here (so long as you continue to follow the instructions for insight), can hardly go wrong.
when you go on the goenka retreat, spend the first three days observing your breath and the sensations around your nostrils/above your upper lip in an insight (moment to moment) way. then on the fourth day, when the technique changes to observing bodily sensations, switch to observing sensations and make sure to continue doing that in an insight way, which is what you will then be explicitly instructed to do (by the emphasis goenka places on observing impermanence, anicca).
tl; dr: just do insight practice.
tarin