Protected or unprotected 18650s for Manker E14 III?

I just bought a Manker E14 III NW,which I love.
(I'm getting a 18650 extension tube for it.)

(The included 18350 battery is a little low-capacity,though).

Would a protected or unprotected 18650 battery be better?

https://www.batteryjunction.com/sanyo-ncr-18650ga-button.html (protected)

https://www.batteryjunction.com/sanyo-ncr18650ga-li-ion-flat-top-battery.html (unprotected)

E14III 18650 tube is designed to fit around Manker proprietary battery.
Any aftermarket battery, protected or non protected, will be either too long or too short
Buy the 18650 tube and their 18650 battery and save yourself a headache

I have the E14III and use it exclusively with the 18650 tube. I have rotated several different length batteries through, both flat and button top. All worked well and with a spring at both the head and tail, the light seems to be tolerant with regard to length of the battery in my own personal experience. Currently, I am running it with a Samsung 30Q flat top. I have also successfully used LIION Wholesale 18650 3000mah Button Tops, which are a rebranded Samsung 30Q button top. I have also verified a Sanyo NCR18650GA flat top as well as most of my 16650s in a sleeve work in the light. This is not say that every 18650 will work in the light, just that every button top and flat top 18650 (and 16650) I have on hand work in the light.

The thing is,I bought the light first,and later decided I wanted the extension tube for 18650s.