IMHO the core batteries are so small, that they really aren't worth it. Many looking for portability are spending more money and going with some of the better starters that can take more than twelve volts and using two of the sub-C 6 or 7 cell 3300+ NiMH packs in series. The Sullivan Dynatron will take up to 24 volts. There are also many smaller geared units out there that work well this way.

I have one of the units you are considering sitting on the shelf in my hangar, it is collecting dust. I even replaced the Hobbico gel cel battery with an Interstate battery of the same size, with a higher amperage. The performance was still lack-lustre to say the least.

If you are looking for a strong but reliable set up, get an inexpensive motor-cycle battery that has 12 amps or higher rating, or even a small garden tractor battery (135+ CCA rating). These will give you enough amperage to start up to and greater than 1.20 four stroke engines. My dynatron on a 235 amp ($30) Walmart battery will start my Moki 2.10 and MDS 2.18 with no problem. You can put the battery in a wooden box or plastic container and make a rope, or wooden handle for it. Some even come with an attached plastic handle. Nothing gets more frustrating than a starter that won't crank it over on the last couple flights of a near perfect day!!