GRUB2 chainloading GPT NetBSD partition

[beaker%sdf.org@localhost (beaker)]

Hello,
I'm having trouble setting up GRUB2 chainloader booting of a NetBSD system.
Booting using 'knetbsd /netbsd [-OPTS]' works okay but this doesn't seem to
provide a way to pass options like "userconf=disable i915drmkms*" hence the
interest in chainloading.  I seem to recall successfully setting up GRUB
chainloading in the past but it was for a MBR disk; current disk is non-UEFI
GPT partitioned (see below).  Platform is amd64 but I'd also like to do this
on i386 if possible.

My disk info:
--
$ gpt show -a wd0
      start       size  index  contents
          0          1         PMBR
          1          1         Pri GPT header
          2         32         Pri GPT table
         34       2014         Unused
       2048  617166848      1  GPT part - NetBSD FFSv1/FFSv2
                                 Type: ffs
                                 TypeID: 49f48d5a-b10e-11dc-b99b-0019d1879648
                                 GUID: 85bfa2fa-49ea-4f22-bce3-22229093be5f
                                 Size: 294 G
                                 Label:
                                 Attributes: biosboot
  617168896    7973519      2  GPT part - NetBSD swap
                                 Type: swap
                                 TypeID: 49f48d32-b10e-11dc-b99b-0019d1879648
                                 GUID: 99d1e7ff-6d68-4a98-9dc2-54eba16cfb40
                                 Size: 3893 M
                                 Label:
                                 Attributes: None
  625142415         32         Sec GPT table
  625142447          1         Sec GPT header
--


Working non-chainloader GRUB2 config:
--
menuentry "Kboot NetBSD - method 0" {
    insmod part_gpt
    set root=(hd0,gpt1)
    knetbsd /netbsd -v
}
--


Attempted GRUB2 configs (all non-working):
--
menuentry "chainload NetBSD - method 1" {
    insmod chain
    insmod ufs2
    insmod part_gpt
    set root=(hd0,gpt1)
    chainloader --force +1
}

menuentry "chainload NetBSD - method 2" {
    insmod chain
    insmod ufs2
    insmod part_gpt
    search --no-floppy --fs-uuid --set root 85bfa2fa-49ea-4f22-bce3-22229093be5f
    chainloader --force +1
}
--

Notes:
- leaving off '--force' from chainloader reports "incorrect signature"
- GRUB2 --via 'ls (hd0,gpt1)' -- actually reports a different, shorter UUID;
  neither works in method 2 above.