Any opionion out there one vs the other. I have had the slide since I bought my banjo but it has always bugged me I can’t see the different fret spots, it covers them.
5th string slide vs railroad spikes
Never used a slide before so, not really able to compare.
I had railroad spikes put in my Hatfield when Arthur built it. Love them.
I can see the slide hindering you whereas the spikes are not even noticeable.
I prefer Spikes.
I’m pretty sure you’ll like them better than a slide.
PS, unless you have the skill and tools to do it yourself, be sure to have a ‘competent’ Luthier install them.
Going to have them installed by a great luthier. 7,8,9,10 frets-should I add the 12th as long as I’m having it done.
It’s all up to you, but I don’t see when I would capo up to the 12th fret as I would (try to 
) play in D with only the first string capoed up to the 7th fret.
I only have them on the 7th and 9th fret and that’s actually sufficient, you can tune down to 6th and up to 8th from the 7th fret and tune up to the 10th fret when capo-ing at 9. Not a luthier, but to me it seems there is a risk with every extra spike you have added (extra holes drilled)
I totally agree with what jacqy79 said.
Some folks prefer to spike 7th 8th 9th & 10th.
However, spiking 7 and 9 will get you the same results. You simply tune up or down if need be from the spiked position.
I own 2 banjos, one of which is spiked at 7 and 9, the other at 7, 8, 9, and 10. It’s basically whatever you prefer.
As to your question about spiking the 12th…No, you certainly don’t need to do that. I’ve personally never seen or heard of ‘anyone’ doing that.