Get ready, because you're probably about to see a lot of information about amplifiers and speakers that you hadn't bargained for. I'll try to summarize the things that pop up in threads like this.
1. What matters when adding cabs is impedance, measured in ohms. I believe the smallest impedance your amp can work with is 4 ohms, so one 4 ohm cab or two 8 ohm cabs will be the max you can run with it. First, ascertain the impedance of each cab. Then you will know whether or not it is safe to run both.
2. Just because it is safe to run both cabs doesn't mean it will be optimal. There is a lot more speaker area in a 410 (read: LOUDER) then in a 115, so that little 115 will be struggling to keep up while the 410 will be sailing along. The 115 cab becomes a glorified stand at that point - it cannot keep up with the 410 in terms of volume, so it's only useful feature is that it props the 410 up closer to your ears.
3. You didn't state that you believe this to be the case, but still: Speaker size, in and of itself, does not determine the tone of the cabinet. That 410 of yours, by virtue of having more cone area, will be able to pump out much more lows at higher volume than a production 115 bass cab. Now, manufacturers will often design cabs to play in to this assumption (making 115's that sound darker, 410's that sound snappier), but it's all the other parameters of the box and speakers that create that cab's tone. The only tonal aspect that speaker size has a direct effect on is high frequency dispersion (how far to the side you have to stand before you notice highs becoming less present). Generally, the larger the speaker, the lower in frequency range this beaming effect begins to happen.
You'll also run into things like phasing and comb filtering when running dissimilar cabs, but I think I've hit you with enough technobabble already. I hope I've answered more questions than I've raised. Good luck!