Online Community of Zenith Builders and Flyers
It apparently varies wildly from one FSDO to another as to how much cooperation and "helpfulness" you get from the Feds. I've heard very positive stories and personally know of negative ones. Remember what Reagan said: "The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help'" ;>)
My area had a DAR that had a very good reputation and was familiar with the 750. He was very helpful: my slats were held up in the paint shop and he suggested we go ahead and certify and enter Phase I without the slats. He advised me to get them on during Phase I and accumulate at least 5 hrs so if I ever intended to put them back on again, they'd be a legal mod without having to go back into Phase I. (I had previous flight experience in a 750 w/wo slats and made up two sets of W&B configurations for w/wo slats.) He even preferred to complete most of the paperwork to ensure that it sailed through the Feds, which it did! Well worth the $350! To be fair, years ago I used a Fed inspector (in another FSDO area) and had no problems whatsoever.
So, if possible, ask some recent builders who used the same FSDO you will use about inspectors vs DAR's and go from there!