You need to get properly fitted for length, lie angle and loft. Generally, putter head weight varies with the shaft length. You can add weight using lead tape. A cut shaft can be relengthened with an insert in the grip end.

Optimally, you'd like to get fit but if you can't, pick what length is comfortable to you. If you're in between a 34 and 35, get the 34 since it has heavier weights. That way if you choose to have it extended, you'll maintain swingweight. In general, most players prefer to have the head stay the same or go slightly heavier, instead of feeling lighter which is what will happen if you get the 35 and cut it down. Putters, especially this model, are extremely easy to work on. You also always have the option of sending it to Scotty's Custom Shop for anything in the future if you don't have anyone local who can do the work. Unless you're changing anyway, make sure the repair person knows how to save your Scotty putter grip. It's easy and if you really like the grip, will save you having to find/buy another one.