Isshinryu?

[unknownstyle]

i would think Judo is probably your best bet since isshin ryu is a fairly close range striking art. i would flow right into your natural fighting principles

[StrangeBacon]

Isshinryu would be complimented very well by Aikido.

This.

We mix Aikido in with the karate too, it may be more to your liking since you mentioned you are quite slight and have trouble throwing burly men, Aikido is more momentum and balance based, a big burly man off balance.....if anything his weight is going to work against him

[isshinryu5toforever]

Judo uses the same principles as Aikido. You just learn how to slam people to the ground. I'd say that either one would compliment Isshinryu well, but Judo is generally cheaper and more widely available in the US. I'm a big fan of Judo and what you can learn from it about momentum and body mechanics.

[bushido_man96]

Also in Judo, you will learn more how to break balance in a lot more ways than you will in Aikido. In Judo at times, you have to create the energy to break balance, as opposed to always waiting for it to come to you. This is a more valuable skill, in my opinion, and it tends to be an art within the art.