From what I've been told, these batteries aren't the greatest with electric starters. There are questions regarding the charge rate and peak cranking amps they can deliver.
There's nothing wrong with going for more charge capacity; that could even get you "over the hump", IOW compensate for the slow-motion nature of these batteries. The alternative is going with a newer LiFePo (lithium-iron) battery; those are pretty impressive. The downsides are cost (and they are pricey) and potential for an electrical fire (though that's still an unknown) due to overcharging or/and physical damage. These bikes are hostile environments for electrical components.
IMHO...the bottom line remains the same "what works, works". At the price, what've you got to lose? As long as you're satisfied with the results, I'd call it a successful result. If that only works out because you rarely, or never, use the e-start...it doesn't matter. FYI, though I've never had an e-start engine in one of my CTs, I did run a partial-loss 12v system, supported with a 12v/5.0ah SLA battery. Never ran out of headlight power, as I never rode more than 2 hours, at a stretch, after dark. The only downside is that DTRLs were not possible. I ran that setup for 15 years and better than 20,000 miles, before going to full-wave 70W/12v electrical system and all LEDs. The point of these ramblings is the first sentence of this paragraph...and the fact that there can be many "correct" setups.