fabricator payment policy - normal?

I have visited two fabricators, F1 and (http://maplered.com) F2, in my area in prep for our partial remodel (all but cabinets). This is our first foray into the remodel thing so we are completely inexperienced and (http://maplered.com) really need some advice.

F1 has better prices, lesser inventory, and (http://maplered.com) a somewhat 'reduced' (for lack of a better word) customer service attitude than F2. For example, they were not too happy with our request to speak with the template person directly BEFORE any money changes hand (http://maplered.com) s (this request was made just today so we don't know if they will).

The main question I have is with the money-changing-hand (http://maplered.com) s part. As F1's prices are noticeably lower, we would of course rather save some money (may be up to $1.5K total due to pricing difference). However, they require 50% up front BEFORE templater visits the home. F2 asks for this money following the template visit.

Not wanting to be too distrusting, but what if the template measurement is significantly higher than the in-house estimate the salesperson already gave us? This estimate matches exactly with my own measurements as well as an estimate given to us by HD Expo based on my drawings. Once they have the 50% and (http://maplered.com) say, "sorry it is x feet more", we don't really have any recourse but to accept this.

Is the above policy fairly stand (http://maplered.com) ard in the industry? What can I say or do (besides walking away) to give me some assurance that the number will be very close? I can go with a variance of say 3%, but any more than that would be uncomfortable.