How to handle more 128 byte preamble in Dicom header standard

Hello:

We want to convert our image to Dicom compatible, currently, our pre-
defined device related information is more the 128 bytes which the
DICOM preamble could not handle.

1) Does anyone know if Dicom standard allow us to put some bytes
somewhere else within the Dicom file, for example, does it allow we
define a pointer address at the preamble, and the real information is
after image data (at the end of the file) or before image data
(between the image file and dicom Meta data)?

2) We want to convert 16-bit tiff RGB image to Dicom. How to do that
in theory? Can I just put tiff header in preamle and copy tiff image
data to Dicom image data part or Dicom has its own compresssion format
restrictly by un-compressed or JPEG(lossy, lossless), RLE, JPEG 2000
format

Thanks,

David