more gears on HB3?

Anyone tried changing from the current sturmey archer X-RD4 to 8 speed X-RD8? I love my bike, riding for a couple of weeks now and would like to experiments with higher gear ratio, I got some uphill passages on my treks that give me trouble. I also dont like the shifter that is present on X-RD4. Im not sure what specs should I be looking for to know if the 8 speed version would be compatible with HB3, can anyone chime in? www.sturmey-archer.com/en/products/detail/x-rd4 I was also thinking about Shimano Alfine/Nexus 8-11 speed hubs, but not sure if those would fit HB3. bike.shimano.com/en-EU/technologies/component/details/inter-8.html bike.shimano.com/en-EU/technologies/component/details/inter-11.html www.sturmey-archer.com/en/products/detail/x-rd8

I just upgrade my halfbike 3 with sturmey archer RXL-RD5, but maybe need to change the cog into 14T (now 18T) or should change the chainring due to flat terrain, too high cadence. The original hub is damage due to loss when get pedaling, trying to fix it but does not work. As long your OLD hub is same, it would fit with HB3.