[phenixbb] Phaser SAD module - resolution question

Dear Phenix community, I am using Phaser SAD module with a poor MR model to locate the initial heavy-atom sub-structure. I have a 3A dataset but the anomalous signal is weak at the higher resolution shells. I would like to ask for your advice regarding the resolution I should use in Phaser. I thought that for the sake of just locating the sites I should use relatively low resolution (let's say 3.5 or even 4A) and then run Phaser a second time. In this second run I would use the highest-resolution and let Phaser only refine the sites (located in the first run) during one cycle and calculate the combined phases. Thank you in advance for your suggestions and advice, Peter