Most drives will burn DL media with a DVD-ROM booktype.
If you want to set the booktype to DVD-ROM on SL media, make the drive region free and use various other patches then you can crossflash your drive to a real iHAS120. Check this thread: http://club.myce.com/f44/dh-16a6s-crossflashing-304838/
If you do, make sure you backup both your EEPROM and the firmware first and keep those safe just in case you might want to go back to the DH16A6S at some point in the future.
If you've got a firmware which has not yet been posted here yet (which might well be the case since as far as I can remember only DELL and ACER versions of the DH16A6S firmware have been posted here), then please let us have a copy of your firmware backup as well (you can upload it to a free host such as Mediafire and post the link here). Someone might need it at some point!