If your current Sidi's fit you well I don't see why a larger size won't work.

I wear a full length orthotics in my cycling shoes. I was wearing a 37 Sidi and had to go to a 38 Sidi. Half sizes weren't long enough but width didn't seem to matter. Even with a high instep I have no problems with the Sidi's and my orthotics.

Today I picked up new orthotics made specifically for my cycling shoes. I took my shoes and the insole that came with them. Using the insole as a pattern the orthotic was cut to fit the shoe. Mine are easily trimable.

As I remember my first orthotics were cut to fit my gym shoes. From that model I went out and bought cycling shoes (Sidi's) that fit the orthotics.

If you get a half length or 3/4 length orthotic you may get by with a half size larger. Don't buy any new shoes until you get the orthotic. You will probably have to get new athletic shoes also.

REI had a great sale on Keen shoes. My orthotics work great in them.

Don't try to squeeze the orthotics into the shoes and ride with them. If they are too tight you will get numbness and hot spots.

My knees are so much happier with my orthotics.