sorry…
so my wife has just bought new bike boost front and rear, whereas mine is 100×15 and 142×12.

all fine so far. there is a spare set of non boost wheels lurking about. in a pinch, could i make the non boost wheel set fit the boost bike – without relacing the wheel, so emergency only, so we can share a spare set of wheels

this is what im thinking
FRONT seems simple – 2off 15mm id spacers 5mm wide- and a 5mm spacer for the disk and longer bolts done.
REAR – 2off 3mm wide spacers 12mm id and a 3mm spacer for the disk. leave the cassette alone and just tweak the limit screws – as a bodge – the rim will be in the middle and if its lift assisted she wont need the granny anyway.

question – am i correct in assuming the rim is in the same place re the ends of the spacers, rear boost v. non boost?
http://fcdn.mtbr.com/attachments/wheels-tires/1041357d1452362665-hope-hubs-pro-2-evo-pro-4-boost-not-boost-wpid-pro-2-evo-front-rear-boost-comparisons.jpg
this says they are

question – am i correct in assuming the rim is in the same place re the ends of the spacers, rear boost v. non boost?

Yes the rim is central on the hub in boost, as it is for a normal hub (assuming you dont have a weird offset frame).

You have to re dish the rear if you’re using a boostinator or so I read. Only 5mm or so, I’ve not tried it personally, would imminent death occur if your rear rim was 5mm to one side?

Ignore me, just looked at the diagrams properly, that should be centre. Will the disk be in the right place?

The boostinator kit makes a re-dish necessary because it puts all of the spacer on one side of the hub, not evenly split.

If you spaced the rear hub by 3mm each side your smallest cog on the casette would be 3mm inboard of where it should be, limit screws on mech should allow for that.

But, 3mm & 5mm spacers, in a muddy forest? I’d make plenty of spares!

yeah.

all this is, is a way of throwing a spare wheel if in the unlikely event she breaks a wheel. emergency only, all the bits will be taped in a bag with the spare wheel set in the chalet or whatever.

maybe i should upgrade my bike to boost….

I can squeeze my Nomad 142mm dropouts in or out by 6mm with just finger tip pressure… just saying. Im not convinced a 142mm axke in a boost frame is the end of the world…