I just looked at a 17 Stratos Flats boat and it looks fairly heavy. I would check with other Stratos owners and see what they are using. I just put an iPilot 55 on my 16.4 skiff but the hull weighs under 400lbs.
As mentioned above, the size TM needed depends on the size and weight of the boat, wind, tide and current. If you plan on fishing inlets with a ripping current for snook or tarpon you might want to go with a 24 V. To keep weight and size down go with Odessey 1200 batteries.