You’ve reduced the diameter of the chain ring so you need to shorten the chain slightly to compensate.
Re skipping between 7th and 8th, that has nothing to do with an oval chain ring. It sounds like you’ve altered the chain line in some way. Is the offset of the oval the same as the ring you took off? Did any grime get behind the new ring when fitting it so it’s sitting slightly proud if it is the same offset?
You’ve reduced the diameter of the chain ring so you need to shorten the chain slightly to compensate.
Re skipping between 7th and 8th, that has nothing to do with an oval chain ring. It sounds like you’ve altered the chain line in some way. Is the offset of the oval the same as the ring you took off? Did any grime get behind the new ring when fitting it so it’s sitting slightly proud if it is the same offset?
No grime got behind the new ring , I cleaned and and re-greased all the parts that needed it. Offset is 3 mm on new oval ring which I believe is the same as stock, but not really sure since it says nothing about the chainring specs online for stock….