MEG forward model for eyes outside the scalp

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  • MNE version: 1.9.0
  • operating system: Ubuntu

I want to make a source reconstruction including the eyes and adjusted this tutorial to do so: Generate a left cerebellum volume source space — MNE 1.9.0 documentation

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This works nicely, but after calculating the forward model some voxels of the eyes are lost because they are outside the scull: See n_used

Before (src): <SourceSpaces: [<surface (lh), n_vertices=163842, n_used=258>, <surface (rh), n_vertices=163842, n_used=258>, <volume (eyes), n_used=514>] MRI (surface RAS) coords, subject 'sub-3a53720640b7_from_template', ~190.6 MiB>
After (fwd["src"]):  <SourceSpaces: [<surface (lh), n_vertices=163842, n_used=258>, <surface (rh), n_vertices=163842, n_used=258>, <volume (eyes), n_used=62>] head coords, subject 'sub-3a53720640b7_from_template', ~190.6 MiB>, ok doesnt work because eyes are not in the scull?

I tried to use mne.make_sphere_model() as bem, but this also doesn’t work because

    bem2 = mne.make_sphere_model(r0=(0.0, 0.01, 0.04), head_radius=0.09, verbose=None)

    #%%
    fwd = mne.make_forward_solution(
        full_path,
        trans=trans,
        src=src,
        bem=bem2,
        meg=True,
        eeg=False,
        mindist=-10.0,
        n_jobs=None,
        verbose=True,
    )
    print(fwd)
RuntimeError: Found 15 MEG sensors inside the outermost sphere shell, perhaps coordinate frames and/or coregistration must be incorrect

Any ideas how to solve this?
Thanks in advance!