are you also willing to pay more if it's completed early?
what a builder asks you a pertinent question and it takes you a week or more to make a decision ... does the delivery date get extended to accommodate your answer time?
what if a part supplier delays delivery of your custom order pre-amp (something a builder has NO control over) ... are you expecting the builder to compensate for this delay which is outside of their control?
what if your builder recommends you take a certain path (wood, pre-amp, pickups, and/or construction method) and you insist on something different ... would it then be OK for you to rake the builder thru the mud because your bass doesn't sound/feel/etc... that way you envisioned it would?
just curious ... and in no way am I writing this with an argumentative tone. the idea of a contract as you note is something I am considering - maybe not to cover things to the level of a firm delivery date, but to a level that provides protection to both parties entering into a custom bass deal.
all the best,
R