you really shouldn't need to mess around with naming files with LUN ID's as I don't think the Macintosh OS really even know anything about dealing with LUN addresses (someone correct me if I'm wrong here), the LUN feature is really just a hold over form the original Zitto firmware for the sharp X68000 computer that the bluscsi is based on. Nor should you need to specify the sector size unless you are doing something very uncommon. 512kb sectors are pretty much always used as its the best speed/perfomance/file size ratio for the older systems. I'm not actually sure if the bluescsi supports say 1k or 4k sectors but its certainly not something id recommend messing around with regardless plus if would likely have a negative effect on the R/W performance.
Look personally I don't even use the bluescsi device myself, I tried it out along time ago, but found the performance was kinda average in about in the middle in terms of transfer speeds when compare to other solutions. but more importantly the Bluescsi isn't electrically designed well. I ended up making a better carrier board for the bluebell with actual line drivers and protection etc but I never bothered to get the PCB's made due to the performance not being as good as my other scsi HD emu devices.
I'm not sure what electronic engineering skills Eric (the guy who makes the bluescsi) has and maybe his day to day life/job keeps him very busy but I've tried to mention to him in the past some of the issues and simple fixes he could implement and I also know other people have contacted him about these things too.
Honestly that was over a year ago now and I'm not even sure he really comes on the forum here much if at all these days. Im just speculating here but I get the impression that he didn't like feedback he got and there was a little hostility towards him by people due to the responses he gave.
I only mention this because as
@Daniël mentioned there may be better resources out there to get more info about the bluescsi and how to use it/set it up etc. I'm always happy to offer what advice I can to help out but as like I mentioned I just don't use the bluescsi devices at all these days.