resample scenery masks not working


I forked ortho4xp and am in the process of modifying it to support fsx/p3d. I am having trouble getting blend masks working, and I have a couple of questions.

1) Can we use BMP images for blend masks? I looked at how FsEarthtiles does it, and it seems to use BMP images. Other places suggest 8 bit gray scale TIFFS, though.
2) Can the mask image be a different pixel size, and cover a different area than the bmp files used for creating the terrain? The way Ortho4xp creates masks files is that it will create one large mask file covering the whole area, but multiple individual scenery files depending on the resolution (the higher the resolution, the more bmp files created for the actual scenery).
3) Here is one of my inf files, does it look incorrect?

Type = MultiSource
NumberOfSources = 2

Type = BMP
Layer = Imagery
SourceDir = F:\ortho4xpvm\Ortho4XP_FSX_P3D\Orthophotos\+25-081\USA_2_13
SourceFile = 3472_2240_USA_213.bmp
Lon = -81.5625
Lat = 26.431228064506442
NumOfCellsPerLine = 4096 ;Pixel isn't FSX/P3D
NumOfLines = 4096 ;Pixel isn't used in FSX/P3D
CellXdimensionDeg = 0.000171661376953125
CellYdimensionDeg = 0.00015413498105910917
PixelIsPoint = 0
SamplingMethod = Point
; pull the blend mask from Source2, band 0
Channel_BlendMask = 2.0

Type = BMP
Layer = None
SourceDir = F:\ortho4xpvm\Ortho4XP_FSX_P3D\Masks\+25-081
SourceFile = whole_tile_blured.bmp
Lon = -81.5625
Lat = 26.431228064506442
NumOfCellsPerLine = 16384 ;Pixel isn't FSX/P3D
NumOfLines = 16384 ;Pixel isn't used in FSX/P3D
CellXdimensionDeg = 4.291534423828125e-05
CellYdimensionDeg = 3.853374526477729e-05
PixelIsPoint = 0
SamplingMethod = Point

DestDir = F:\ortho4xpvm\Ortho4XP_FSX_P3D\Orthophotos\+25-081\USA_2_13\ADDON_SCENERY\scenery
DestBaseFileName = 3472_2240_USA_213
BuildSeasons = 0
UseSourceDimensions = 1
CompressionQuality = 100
LOD = Auto,13
I think the culprit was #2. I switched to v130 of ortho4xp which generates masks which cover the same physical area as the satellite bmp, and it works fine now.