I had SPD, i was hoping for a waterbirth but ended up being induced and fully monitored due to waters breaking with no contractions so couldn't use pool.
During labour i didnt notice my SPD pain as the labour pain defo took over but i went from 0-10 cm in less than 4 hours so was obviously quite quick.
I did have an epidural but only near the end (think it was too late really but they didnt realise i was as dilated). I told mw about not having my legs too far apart and they were really good about this....
until...heartrate of DS dropped and stayed low so i had to be examined by Dr, who basically ignored by feeble protestations about my legs whilst she rummaged around, i ended up with an emergency cs so was then no longer an issue as far as SPD concerrened.
My SPD was immediately improved, i went from walking with lots of pain/difficulty pre-birth to feeling much better by the next day even with cs wound, this was sore but personally found it a much easier pain, didnt grind through you iykwim.
Could you discuss with your mw the possibility of attemping natural birth (with epidural if you need as long as they are aware of max width of your legs) but in the event of complications could you ask for immediate cs rahter than forceps or ventouse for which i imagine they will have to abduct your legs. I guess it depends how bad your SPD gets at the end on how strongly you may feel about this.
I am pg again and think i am going to ask for elective c-section as am v. worried about SPD as it seems it may be worse second time. Im only 9 weeks though so obviously will wait and see how things pan out. the whole cs vs vbac thing is a whole other issue anyway!!
There are lots of SPD management tips on here if you search, a recent one that seems good is getting a memeory foam mattress or mattress topper (cheaper option).