Bright post-it on the front of your notes saying "I have SPD - knees must NOT be parted more than x cm AT ANY TIME"
Put partner in charge of ensuring this and demanding any internal exams be done on your side/seated.
I laboured in the pool in the MLU which was great except they made me get out after 8 hours of nothing happening. And then somehow the SPD got worse which is very rare and impressive given as I was in a wheelchair beforehand!
At this point the MW said "You know how you were scared of an epidural - would you like to reconsider?"
Epidural was fab! Did some pushing on all fours, had ventouse in the end and ds popped out. We were supposed to have a loop of string to keep round my knees to ensure no-one could open my legs but we lost it on the way to hospital.
And I recovered really quickly from birth though we should have ensured the hospital knew I was on 60mg codeine 4x daily, as I didn't get any until 36 hours after birth, by which time I was shouting "Why does everyone keep asking how my vagina is? My vagina is just fine thanks now get me some codiene for my hips!!!"
Or, y'know, just taken some from the stash in my bag, but we weren't very with it.
Postnatal exercise classes were excellent too - I was as fit as I've ever been by 3 months post-birth.
Maybe take extra pillows and an extra birth partner with you - hoiking me onto a mountain of pillows was quite an acheivement, but my birth was as good as a long labour could be.