This is a good plan. Either will start working quickly. Prop will still take a wk or two, where as TNE will work instantly. The only issue is, you'll be increasing your overall weekly dose of test. The tricky part will be when to come off the short acting test, so you don't build your levels up, only to dip down in week 5, 6 or 7. For this reason, I would keep the dose low. Even though TNE doesn't have an ester, it will build up in your body and take several days, if not longer to lower back down. For this reason, I would go with about .5cc TNE ED about 2 hours before training. This will quickly raise your test levels. I would use it for about 3 wks.
Just make sure to rotate your injection sites.