Yes, in effect, you are now running 8TC, especially if you have twisted the runs together. I have done this in single wire configuration with one double run of 4TC on one speaker and a single run of 8TC on the other, twisting the double run of 4TC, and I can hear no difference between one speaker and the other. If you do a search at Audioasylum, there are posters there who feel that double runs of 4TC not twisted (simply run in parallel) outperform regular 8TC, but I have no experience with that and can't comment.
In any event, I'm sure you will be fine.
In any event, I'm sure you will be fine.