If you use the 4x4's, tack on those HDPE plastic glides on them. That will make it a lot easier to slide them. Teflon is very similar to HDPE but it has less abrasion resistance.

https://www.boatoutfitters.com/trailer-bunk-slides

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).