Seems quite low - you could try with higher values, and if there is no problem sitck with them. I'm using currently 0xffffffff as Mask and 0x00ffffff as Max Transfer. Block size depends on used filesystem, with SFS it is recommended to use 512, with PFS3 you might want to try 1024 or even 2048 (not so sure about this since I'm not using PFS3).
I recommend you to do some search on Maxtransfer here on a.org and aw.net, there's quite a lot of more exact information about these values. For example here (
http://www.amiga.org/forums/showthread.php?t=23415).
Edit: You can change maxtransfer and mask on the fly without formatting, but changing blocksize requires format I think. First time I tried to change maxtransfer and mask with hdtoolbox they returned back to original values after boot, so they never changed. Using SCSI tools for Cyberstorm were able to do real changes.