Slow Stick
The problem is not the MAH rating of the battery.
It is the fact that it is a 7 cell Nimh battery.
Most of the time when you go from a Nicd pack to a Nimh pack you need to add one additional cell to keep the amount of power the same. There are newer Nimh cells which do not pay this penalty.
An example of this are the battery packs I have for my Zagi. I have 1, 1700 mah Nicd pack, 1, 2700 mah Nimh pack and 2, 1700 mah Nimh packs. All of these are 8 cell packs. The 1700 Nimh packs produce the most power. They are of the new cell technology and are capable of supplying a good high current. The 1700 Nicd pack is OK. The 2700 Nimh pack has the longest run time by far (almost double), but not near the speed, because the pack just can't supply the current the motor wants.
Basically your 7 cell 1100 Nimh pack will probably perform like a 6 cell Nicd pack. For me that will not be enough snort for the plane.
My advice is to fly the plane with it and see how it performs. If it does great, then it works. Enjoy it and don't worry about it. If it doesn't perform so great, then that's OK to, you haven't lost anything.